WIBTAH? Cousin invited me to be part of the "something blue crew" and I don't know how to respond.

Long story short, my cousin (F21) is getting married sometime in the next year and a half. She texted me (F25) and asked me to be in her something blue crew for her upcoming wedding. I had no idea what this was and asked her and her response was that its "an important role for family members and friends". I didn't want to cause problems for her, so for now I agreed, but I've taken some time to reflect on it and decided to dig more into it.

Turns out the something blue crew is more like the help at a wedding, people that aren't necessarily important enough to be in the wedding party. I'll admit, it really hurt finding that out. I got married a few years ago and I had such a hard time picking between her and my best friend as to which of them would be my MOH and a bridesmaid. To learn now that she doesn't see our relationship in the same way hurts. And before anyone asks, she is having a substantially large wedding (150+ people) and I know from another cousin that she was asked to be a bridesmaid (there is 5 of us total that are cousins counting the bride and another one is her sister, confusing, I'm aware).

More or less, learning that I've been asked to be the help is frustrating, but I do understand that it is her wedding and I will respect her decisions. However, she said she might ask for financial help from me and my family during this. I just don't know how to feel about my assumed role and being asked for help in that way. Honestly, it makes me not want to go to this event. Her main reason for why she didn't select me to be a bridesmaid is because "it would be too complicated". I don't know how or why it would be too complicated. I expressed my feelings to her, but she just said it would be complicated.

So good individuals of Reddit, WIBTAH if I decided to not go to the wedding? Granted it is a year-ish out, but still. I don't want to punish her for her choice, but it hurts a lot more than I thought it would. I'm kicking myself because I'm more of an adult than she is, I need to be more understanding and respect her choices, but I'm really having a hard time here. TYIA!