My 22F friend has been keeping secrets from me 22F

I don’t know how to start this other than just get into it. My very close friend who has been in my circle for the past few years is a really kind and smart person, and this is really unlike her. A few months ago I was dating this guy 22M for a month because tahts all i could manage. He was so kind and a great person until we started dating. He started trying to make everything physical as much as possible and just made me so so uncomfortable by the way he acted towards me. My friend, let’s call her E, was one of the people I first told when I broke up with him and how horrible and uncomfortable he made feel. Then, just a few months or maybe even weeks later my ex, let’s call him B, asked out my really really close friend, who also happens to be E’s twin sister. After my friend, thankfully, said no, E again, immediately jumped onto how weird that was and how weird he was in general. Now, guess who E is talking to. Yeah that‘s right. B. I really don’t know what to do because it wasn’t even E who told me, it was her twin sister. I don’t know if I should confront her, or just let it happen and she can experience the agony i felt when I was with him. Anyways, just wondering what you guys think i should do!