mil seems wholly dissatisfied

Is she doing something specific to make you feel this way? Sometimes you can just get in your own head and think that someone is acting a certain way, especially with all of the stress of planning. If she is doing something in particular, I'd suggest sitting down with your fiance and discussing the behavior, but make it more of a how can you help to make his mother feel more comfortable so he doesn't think you are attacking her. Sometimes just doing that will bring to light that his mother might be acting in a way that isn't acceptable and he may take care of it on his own. You should not be holding things back, that is only going to make your relationship with both of them worse. So I would highly suggest you talk to him about how you're feeling.

So my fiance's mom is a big saver, and she ALWAYS comments on how people are spending too much because it's just her way. We've learned to ignore that. A lot of people don't think you should spend a ton of money on a particular day, so as long as you're comfortable with the amount, you're fine. I would tell her that too, we are comfortable with this amount and we have worked out a budget already.

As to the disinterest in wedding stuff, some people just don't get into it as much. My own mother is actually one of those people. She's not really into the whole planning thing with me. I started inviting her to things that she would enjoy and planned things that I knew would get her excited. For example, we made an entire day of going out to find a dress for her and she had a blast and really got into it. She is also going to do our cake tasting with us and is very excited about that. But even when I went to try on dresses...she wasn't really that interested. It's just not her thing. Maybe talk to your fiance about things she might enjoy so you can include her in those things? That way you're not leaving her out, you're just selecting things you know she'd enjoy being included in.

As for talking about it, you need to. Whether it hurts his feelings or not, you need to express yourself to him and make sure he understands that you are trying and you aren't sure what else you can do. If you don't, things are only going to get worse for you. Nobody is a mind reader and communication is very important. He can't help if he doesn't know it's bothering you.

Honestly, I would stop trying to include her if she doesn't seem interested. We didn't share any information on how much we spent because my mother-in-law definitely would've made comments. My sister-in-law warned me not to share too much with my mother-in-law because of comments she made when my sister-in-law was getting married. I also wouldn't let her steal your happiness. She will have to eventually learn to accept that you guys are getting married.

I know, the struggle is real to bring things up that bother you because you don't want to upset anyone! Especially when this should be a happy time in your life. I truly hope that talking to him helps and you can enjoy your engagement more! Best of luck .

From your post and responses, it really seems like you are making a lot of assumptions about what your future MIL is thinking and feeling, while also expecting your future spouse to read your mind/make assumptions about what you are thinking and feeling.

I agree with all the previous posters who recommend cutting back what information you share with her. Don't volunteer wedding planning details and if she asks, keep everything superficial and general. Also, I would stop trying to "force" her participation (I know you aren't forcing her, but you keep inviting her and then getting upset when she continues to show no interest; stop inviting). There are no rules that all family members need to be engaged, excited, and involved with all the ins and outs of wedding planning. Allow her to remain disinterested and you will be much less disappointed.

You need to communicate with your future spouse, about wedding planning and all important things in your life. These statements indicate deep relationship problems that should be resolved before you get married. "Because of my feelings and not expressing them, I’ve been pulling back from them both out of fear that I’ll say something I’ll regret if triggered in the slightest way. I want to spend time with my fiancé, but not at the expense of this weird dynamic that will get worse as the engagement continues." If you can't be open and honest with your spouse, what's the point of getting married?

And finally, try really hard not to read into your future MIL's actions or guess her thoughts. If she says or does actual problematic things, then ask your future spouse to handle those incidents. But don't "borrow trouble" but deciding that she is "wholly dissatisfied" with no actual evidence of that.