Search Results: seeing significant other

I have two dilemmas. The first one involving a fake person and the other involving an obnoxious one.

The first girl happens to be my second cousin (don't know how significant that is) and to keep it short I warned her about crappy guys she was hanging out with and she told them what I said and they all lashed out at me. She acts like we're cool now and always talks about me being her favorite cousin, only friend, etc. when she hasn't even apologized for the problem she put me in. Part of me really wants to confront her actions and the other part of me suggests to be nice to her and act like everything is cool. I don't care about my relationship with her I just want to pick the way that makes her look more fake. She already knows that I found out she told the sketchy guys what I said about them, but it comes down to if it's worth confronting her or not.

The second girl is just a bitch ex who wants to see me at my lowest. I finally found a girl that I might date and the moment I start talking about her she says my potential girlfriend has a weird name (she knows we are seeing each other). She does similar stuff like this whenever I see her and I would avoid her and the first girl I talked about but my family is good friends with both of them so I spend a lot of time with them. The question here is if it is fair game to bring up all the shady stuff she's done in the past? She sent nudes to a guy that had a girlfriend while she had a boyfriend as well as attempting to hook up with a guy that has a girlfriend. If she pulls a bitch move with me like making fun of my potential girlfriend's name, would it make her look worse if I play it off cool or bring up all the shitty stuff she's done in her past?

At this point I have kept my cool with both of them.