My father is walking my step-sister down the asile!

It's bothering me that people are telling you that your feelings are not valid and to get over it. Your feelings are indeed valid. While I have not been in this situation, I feel for you and what you are going through. No one knows your relationship with her nor your step mom to know what has brought you to thinking that she might be doing this to be spiteful. As other's have said, I would talk this over with your father in private. I wish you the best in this.

It sounds like your step mother is a horrible person, and I am sorry for that. Have you ever talked to your dad about the way she treats you? Does your step sister treat you badly? I guess that is the thing I haven't seen you post. It's not her fault her mother treats you badly. It's also not her fault that your dad lets his wife treat you so badly. I understand your hurt, but it seems you are misdirecting the hurt your step mom's causing you towards her. You should definitely have a talk with your dad about your feelings and sees what he says. I would focus the talk on your relationship and the way your step mom treats you and not about him walking your step sister down the aisle. That is not your real problem. Your real problem is your step mom is a horrible person and your dad hasn't been willing to stand up to her for his own child. Once you work through that with your dad, I don't think it will bother you as much that he's walking your step sister down the aisle.

I truthfully do not see how this is upsetting you THIS much. A little background, my older sister and I are technically half sisters, different Bio fathers, she knows her bio and has been in contact with him, but my dad pretty much raised her. She has been married twice now and each time my dad walked her down the aisle (second time she had someone take a pic for her to send to her bio as a "I don't need you"), I am by no means upset that my dad has walked his EX step daughter(he and my mom have been divorced for 21 years now) down the aisle twice, if anything I feel that it's special that my older sister and I get to share the honor of getting to make that walk with him. The mentality of "he's MY dad how dare she?" is truthfully kind of adolescent...especially since your weddings are about a year apart, she is by no means stealing your thunder, and instead you should be happy for your father that not only does he get to walk HIS bio daughter down the aisle but also your step sister. If you don't know the relationship she has with her bio, then it probably isn't good, especially if she is asking your dad to walk her instead...

I hate to be blunt, but this is really a matter of you need to look past the teenage mentality of he's just your dad, and look at this from their point of view, he is probably extremely touched that she asked him and that he gets to walk BOTH the girls he sees as his down the aisle and she is probably just relieved that she has someone to make that walk with her.

The person that you seem to really have an issue with is your stepmom...not your stepsister, you can't blame her for how her mother has treated you (trust me I DO NOT get along with my step mother, I get the evil step mom thing...I call mine the Hobbit, and am not happy that I'm paying $30 for her to have a corsage at the wedding) but it's not right to direct your anger and frustrations that come from your stepmom to your step sister...and if all of this is bothering you THIS MUCH, you maybe need to take other's advice and maybe talk to someone about it, therapy definitely has a stigma behind it BUT can actually do wonders (and help with the stresses of wedding planning!)

I hope that you can move past this and that the rest of your planning and marriage go beautifully!

At least her wedding is in June. Once it's over, everyone will forget about it and the attention will be back on you and your planning. I can understand how he is YOUR dad and you want to be first. But in the long run you have more time to plan your wedding with your father's support. Make lasting memories during that time and he will remember his only daughter's wedding more than anything else. Because the "only" is just as important to him as it is to you.