My cousin is a what!?

So, I am (F), and last year, on December, I went to my nanubari with my family as usual but this time it was a little different because there's a big gathering hosted by my aunts (Including my mom) I mean they all together hosted it and paid for it and invited all others family, distinct family members and many people..So my mom has a cousin, (chachato bon, um lets call her 'gajor'). Gajor has a son and a daughter (Let's call the daughter mula). So mula is in college second year, pretty rude and moody almost to everyone, she also doesn't like to wear traditional outfits, always stays like tom girls, thats fine, I myself don't wear traditional clothes except for eid or wedding invitation and I also find baggy clothes comfortable, but she? She directly says traditional clothes are 'bosti' (Wtf is wrong with her)..She also had long and shiny hair (I was jealous of her hair tbh) And she cut it short, like you know boy cut? She cut her hair like that.. The thing is, when I saw her at the gathering, I noticed she was oddly nice, not to everyone but me. And she was also looking at me occasionally and complementing me. So when all the cousins were taking pictures together, I stood beside her, as we were taking pictures, she suddenly touched my waist, which I thought was okay, just holding me, but then slowly, she lowers her hand and starts to touch my..Ass. and her hand was moving like circles like she was enjoying it, she even squeezed it. I glanced at her, looked back at people who were taking pictures, and gave an awkward smile, just for the picture... I realised that she might lesbian. (Astagfirullah). The rest of the day, I didn't talk with her or even go near her, At night I told my sister about it and she brushed me off, not believing it, the next day, I was hanging out with my other cousin who is actually close to mula and used to be in the same school as mula, so I asked her about mula and she conformed it, that mula is actually lesbian, and she even dated girls when she was in school, I was stunned, my sister who didn't believe me was stunned, and now the thing is, mula is trying to contact with me through social media, but I don't want to talk to her, I am Muslim and astagfirullah, I would never..She is also Muslim but I don't why she is like this...I can't even say anything to anyone.. I can't even say directly say no to her face, knowing she will make my life hell if I say no... What should I do?