It's just how I feel on the inside

Maybe this is weird but I just found out that my fiancés sister is still good friends with his ex of 5 years.

And I'm not sure why but it makes me feel weird on the inside. I dont think angry is the word but I don't like it and it makes my insides uncomfortable.

I'm a very doubtful person unfortunately I've been through the ringer, I've been hurt and betrayed numerous times and I'm definitely affected by lots of things piled up over the years.

My fiancé didn't do anything wrong. I have no issue at all with him. I just dont like the idea that his ex is still connected to the family I'm marrying into. I get inside my head. It makes me not want to tell her my business and be close to me because I dont want her gabbing to his ex.

His sister is pleasant but even my fiancé is aware that me and her dont really click. And she was apparently "hurt" that I didn't consider her to be a bridesmaid (sorry but the bride tribe is made up of people important to the bride and I barely talk to his sister we are not close so no I never considered her to be a bridesmaid and I'm not obligated to have her as one) just a tidbit of info there. I just get inside my head and worry and wonder if she's talking shit or just our business to her friend who is also his ex. Like I don't even want to get her a Christmas gift because it rubs me the wrong way. It just bothers me that someone who hurt my fiance so badly back then is still friends with his sister who is fully aware of how it all went down - like I would never be friends with my own siblings ex if they cheated on them and treated them terribly.

It bugs me. I know it isnt my business or there is nothing I can do - I just needed to vent and perhaps hear some outsiders opinions - even if its someone telling me that I'm whack for thinking and feeling the way I do.