How do i turn down my cousins offer to make me a flower girl at her wedding?

Im going to make this as short as i can but its a long story.

Background: My cousin originally asked me and my sister to be bridesmaids st her wedding. Fast forward and we do not get the bridesmaids official invite. Fast forward My sister (my sister as hurt by this. She is very close with my cousin. I couldn’t care less but the lying was annoying) has a conversation with my cousin on fourth of july and she explains that she had to many people and feels bad she couldn’t make us bridesmaids. My sister suggests doing something else like making us unofficial bridesmaids, having us wear the same color, or simply attending the bachelorette party/ joining them in the changing room before the wedding. Fast forward my cousin sends me a vase of roses and asks me to be a flower girl.

Why i don’t want to do it: im 28. At the end of the day its tacky and a degrading I’m not a five year old girl. i would suck it up normally but, this particular wedding is going to be hell for me. Out of all my siblings and cousins i am the only one that will be attending single. I have always struggled with dating and every time i am with my family i always get the typical questions about my love life. Its horrible and sadly it makes me hate being around my family even though i love them. Its incredibly embarrassing that im going to this wedding alone. In addition to this my cousin is unfortunately very good friends with a lot of the girls from my sorority in college who were not very nice to me. I wouldn’t go as far as to say they bullied me but i was harshly outcasted in my sorority in college by these girls. Its an understatement to say i am not looking forward to seeing them. In conclusion I DO NOT WANT TO WALK DOWN THE AISLE AS A FLOWER GIRL. i don’t want the attention on me at all. I don’t want to be a subject at all. I would not be going to this wedding period if i could help it but my family would slaughter me if i skipped it. My goal for this wedding is to be a wallflower. Im going to say my pleasantries congratulate my cousin and get the hell out of there as fast as i possibly can. There is absolutely no way i am going to be a flower girl.

How do i let my cousin down easy? How do i go about this? Shes a very nice girl and she tried to include me but i don’t want to actually be included. I dont wsnt to hurt her feelings or make her mad. My family is also HUGE on manners they are not going to be happy with me but facing their backlash is the lesser of two evils in this case.

Also if anyone has a magical answer to help me get out of going to this wedding at all please do tell! Lying is not an option tho haha.