WIBTA if I refuse to be my sister’s maid of honor?

Using a throwaway because I don’t want my family or coworkers finding out about this post. Obligatory “English is not my first language”, “sorry if this is too long”, but I need to give you guys the right context.

I (F28) have a strained relationship with my mom (F49) and sister (F23). For context, my sister and I have different fathers. My mom had me young and I was the result of a brief relationship, while my sister is the child of my stepfather (M55), which my mom married when I was about 3 years old. This has always affected our dynamic. While I was a “difficult child” to deal with, my sister was my mom’s little angel that could do no wrong. It would even get to a point where I would be punished every time my sister would misbehave, because “it was obvious I was the one setting a bad example”.

A few years ago, I moved out of state for a new job opportunity. The distance naturally created some space between me and my family, which ended up being good for my mental health. I’ve been doing better since then and have built a life where I feel more stable and supported.

Last week my sister messaged me out of nowhere saying she needed to discuss something important. I had a virtual meeting with her and our mom (they still live together) where they told me my sister was engaged. I congratulated them, but then my mom surprised me by saying my sister wanted me to be her maid of honor. I was caught off guard and didn’t know how to respond in the moment. We don’t talk often, and my sister and I aren’t particularly close anymore, so the request felt sudden. My mom spoke as if this was already decided, emphasizing how meaningful it would be for “the family,” while my sister seemed to assume I would say yes. I asked for some time to think about it and left the call.

Over the next days I’ve been receiving a lot of messages from mom saying how important it would be to have the family together again, and how my sister could use some help with planning the wedding. My sister sent me a link for the WhatsApp group of the wedding party, as well as other wedding requests, as if I had already decided to participate.

The thing is, I don’t know if I want to. As I said, my sister and I aren’t close. We’ve barely had a relationship. Being her maid of honor would require a level of emotional involvement, time, and presence that I’m not sure I can give honestly. It would open wounds I worked hard to try to heal over the last few years. But I also know that refusing would cause a lot of tension and likely be seen as me “ruining” an important moment for the family.

I haven’t given them an answer yet, but the pressure is increasing and I know I’ll have to decide soon. Part of me feels selfish for even considering saying no, especially knowing how much this matters to my sister and my mom. Another part of me feels like agreeing would mean ignoring my own boundaries again.

WIBTA if I refuse to be my sister’s maid of honor?