Future Sister-in-law

In all honesty, I think you are creating your own unhappiness by: 1) expecting others to be overly excited about your wedding, and 2) doing kind acts with the expectation they will be reciprocated.
It was kind of you to pay for the flower girl and ring bearer attire, but that is considered standard for many people. In my wedding (and the weddings of all my family and friends) if are the one requesting them to be in your event, then it is proper etiquette to pay for the wardrobe you are requiring them to wear. Especially for children. You say you offered to pay for HMUA for FSIL because you “want to show her you care and do something nice for them”… but then you say you are mad because it wasn’t reciprocated. If you were truly doing something kind strictly to be kind, then you shouldn’t expect them to “even the score”. It may be disappointing, but no one is going to be as excited as you are about your wedding. But just because she isn’t behaving the way you’d hoped, doesn’t mean she’s not happy for you. I would let these hard feelings go and stop “keeping score” in relationships.

I don't think you are wrong to think this, common courtesy on her part is lacking. Maybe ask your FH to talk to his sister (or brother about his wife) to see if there is something wrong. You've said she isn't warm, but seems like you've been part of the family long enough to have her warm up to you.

I can understand why your upset but I also understand the other side. Your wedding is extremely important to you but that’s not the case with family. My sister in law didn’t reach out either- her daughter was my flower girl & her son was the ring bearer. Wedding planning took the majority of my time & was so important to me but I can’t expect it to be the same for others.

View Quoted Comment I agree with this. Some people are not open/outgoing/friendly or invested in your life but that doesn’t make them bad. Give her space without any pressure and don’t keep score because you will make yourself more bitter. Maybe she’ll come around after that.

I agree that you are creating your own happiness. My sister in law was my bridesmaid and she didn’t text me during the wedding process and it’s ok! I married her brother, not her, and it doesn’t mean she’s not super happy for us. It’s true that not everyone will be extremely excited all the time about your wedding but I’m sure they still love you and care about you.

It seems like everyone is aware this was an “obligatory invite” which usual result in disappointment. Did you and her ever previously have the type of relationship where you called and texted each other privately? As far as not offering help, she doesn’t really have to. I guess I’ve been on the other side of this. I was a bridesmaid for my (now) SIL and aside from her asking my dress size and things like that, I wasn’t reaching out to her to ask about wedding planning. We’re family by marriage and enjoy each other but aren’t necessarily friends. This sounds similar.

My SIL was a groomswoman to DH, and I don't recall her talking to me ONCE about the wedding.

While I think she should have let you know that the kids' attire had arrived, since she's not actually in the BP, it really doesn't matter if she doesn't ask/respond, unless it's about the kids.

Not to say that is how it should be. I would rather get along with in BIL and SIL and all sibs of my hubby. But 10 of them, I do well not spitting in their faces, so I smile, nod and barely speak when we meet, and I feel an absence of hostility is great. These folks are prejudiced by race, religion, ethnicity, and sexists and are outwardly nasty to anyone who is gay,or Morman or Amish. Not reaching out is a sign, someone does not care. But consider the alternative: she is not actively mean. Or maybe she likes you, but has no interest in weddings. Some people don't.
There is no requirement that relatives by marriage want anything to do with the other family. It is a choice. ... I do get along very well with 5 of hubby's brothers and sisters, and all 5 of their spouses. There is no hatred or prejudice there, and they are all reasonably intelligent, and people can agree to disagree without any ranting, or one bunch threatening the other.
I like these people and invite them over often. But, I still do not talk work, or do any of the SIL hobby stuff, or go to movies with them. I just have no interest. They keep trying to get me interested, and we do get along over many things. . Or course, they mostly have nothing to do with my activities either. Lack of interest. But that is okay. No rule says you have to want to like to do things you go not like, just because it is your SIL.... What you need to decide is if you have to have everyone around you like and be interested in everything you do. Or take offense here with SIL where nothing evil is directed at you? Are there things she likes to do that bore the heck out of you?

Were you close ore wedding planning? Do you spend time with her and her family?
Maybe this is a difference in family of origin dynamic, or she’s just not interested in a closer relationship.
I know it’s disappointing that she’s not as engaged as much as you expected. One thing it could be - maybe when she or a friend planned a wedding, people were getting overly involved and she wants to avoid putting any pressure on you? In law relationships can be fraught, and in my view it’s better to have a cordial relationship that is peaceful than one that is rocky.

While I understand that it's frustrating, nothing you've said really shows that she needs to be reaching out to you other than maybe a text about the clothing arriving. My SIL is one of my bridesmaids and her kids are jr. bridesmaid, flower girl, and ring bearer in our wedding. Other than asking them all to be in the wedding and talking about it in a group setting, not once has she reached out to me first about wedding planning. We also plan on paying for the kid's attire because especially for more than one kid that gets very expensive, but I don't expect to get anything out of doing that... she can continue to only show up when I ask her to and that's enough for me.

Try to do your best to let this go. I'm sure she's not doing any of this purposely to spite you or to show she doesn't care. Especially when you mention she has multiple daughters and sons thats like at least 4 kids which is a lot to take care of on a day to day basis... while she's probably not trying to be rude, she most likely just doesn't have time to also worry about the logistics of her brother's wedding.

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This is how I feel. Especially since she's got at least four kids.

You are expecting too much. She’s not doing anything wrong, so try not to be mad at her. I get that you hoped for more, but there’s no real thing that a SIL will be involved in wedding planning. It’s your day and no one will be as excited about it as you. The best thing you can do for yourself is to reset your expectations.

I agree with the others. Not everyone is friendly and outgoing. If that's not her personality she shouldn't be expected to change that for anyone. It sounds like she has a house full of kids and she's probably pretty busy raising her kids to be overly excited about anyone's wedding. My SIL doesn't ask about our plans either and her son and daughter are in our bridal party. Neither does my brother's wife even though she's been part of my family for over 20 years and her sons are also in our party. I'm not insulted in the least. People have their own lives to deal with.
I am very introverted and have often been accused of being standoffish or not doing enough/reaching out enough or in the manner others would prefer. It doesn't mean I don't care about people or what's going on in their lives. I get you're disappointed that your relationship isn't the way you hoped it would be but it's not necessarily personal against you.

If there’s two things to remember in life about relationships it’s that not everyone gets along and that’s ok and not everyone wants to be your friend. You have “tested the waters” with your generosity and kindness and if she is not reciprocating, don’t be too offended. Try to careless or grow thicker skin. She’s either preoccupied with her own life and family or just isn’t interested in going out of her way to be friends with you. Just because you marry into a family doesn’t automatically make you close. Sometimes it takes years for bonds to form or sometimes they never do. I’ve been with my husband for nearly 10 years and I don’t have a relationship with his sister. We don’t text or call or even have each other’s numbers. When we first met I tried to make a good impression and showed up and went out of my way with nice gifts but reality is it was a waste bc our personalities clash. She’s the princess of my hubby’s family and no one will call her out on it even if she’s in the wrong. I won’t be the one to call her out but I won’t participate in her bs so I just avoid her whenever possible