AITA: For knowing my friends friendship would end inevitably

First context: I(21F) have been friends with one of them since primary, I'll call her "Abby". My bestie actually introduced us and we've been friends ever since. We currently have 3 more girls in the group. Now the last one to enter is the "problem", I'll call her "Annie".

"Abby" and "Annie" have gotten so close, they always take about boys and going to see them in other schools, etc. Things me and the other girls didn't really care about, we'd mostly talk amongst ourselves cause they left us out.

The problem started when "Annie" got her toxic POS boyfriend. (They weren't really a thing yet then) Said boyfriend introduced a friend to "Abby" and they hit it off, fast forward they're dating. Then issues started raising, Annie's "boyfriend" said he was sorry and really did try to like her but he didn't (aka leading her on). She was so heartbroken and started getting jealous cause Abby and her boyfriend were fine.

Until they weren't. Turns out Abby's ex was also a POS and they broke up. Annie's ex got back together with her and asked what happened between them (Abby and her boyfriend). Annie told him, he spread it and somehow she still doesn't see he's a POS.

Abby told her why she did that and they fought. She decided to be the bigger person though and forgive her. But the thing is Annie never stopped bringing it up, even when Abby got a new boyfriend. They have ended their friendship (finally).

I personally believe Abby was just friends with her to experience these things with Annie. They are too similar and it just always felt like competition. I really want to tell Annie to break up with her boyfriend but she won't listen, this is their 3rd time back together.

So... AITA?