AITAH for being an AH to someone who was an AH to me first? Doesn’t that cancel it out??

Okay so backstory:
I (F25) dated this guy “John” (M27) for like 7 months and fell SO hard. Like, I dated someone else for 5 years before him and my feelings for John were wayyy stronger. But he was still hung up on his ex and ended up breakin things off a few months ago. I was legit heartbroken. He moved on crazy fast—like, different girl every week fast—and I’ve been tryin to convince myself to follow my head and not my heart. My head knows he’s trash, but my heart’s still dumb.

Anyway, John and my bestie’s bf are roommates, and she basically lives there too, so I still run into him sometimes. And she’ll tell me what he’s up to (even tho it hurts). I swear I wanna be over him, but when I see him, I just have zero self control. We’ve hooked up like 3 times since the breakup. I know, pathetic.

I’ve got a good group of girlfriends (7 of us total). We have a group chat, go out on weekends, went on vacay together, etc. Lately I noticed one of the girls, “Sue,” (F26) kinda pullin away. At first I thought it was from the group, but then noticed it directed to me. One of my friends said Sue is making subtle comments about me, which she never did befor. Then my bestie “Mary” (F26) told me she recently caught Sue sneakin outta John’s room one morning and didn't kno how to tell me. So yeah… Sue’s been hookin up with him.

How it's all come out that it started a month after he and I broke up, but like… I’ve been pouring my heart out to this group and she KNEW how much I was hurtin. I felt so embarrassed. Like, has she been telling him what I'm saying? Have they been laughing at me? Like, I admitted some embarrassing stuff to the group, like becoming obsessed with trying to be more like his ex, and I feel so exposed now. Sue got super defensive sayin I have no right to “claim” John and she can do whatever she wants now. I told her it’s fine (even tho it wasn’t) and tried to just accept it.

They’re not exclusive, but she obv wants to be. Mary even told everyone (with Sue right there) that John’s still messin around with other girls. He has this effect on women.

Then last Thursday, I was out with some coworkers and ran into John. He asked if I was mad about Sue and I played it cool like, “nah it’s whatever.” One thing led to another and yeah… I went home with him. I KNOW. I shouldn’t have. Not even cuz of Sue, but cuz I need to protect my dumb heart.

Now Sue’s freaking out, callin me a bad friend and cryin to everyone about how she’s fallin for him and it's hard enough that he’s still not over his ex from before me (that ex is dating his friend and he's super pissed about that) but now he hooked up with me too. Like girl, you knew exactly what he was like. She cryin about all the things I've been cryin about, but now I'm the bad guy too.

Some of the girls think I’m in the wrong cuz she actually has a chance to be with him, and since he broke up with me I ned to get over him and move out of her way. But most of our friends say we just canceled out each others shitty behavior. It’s not like this was the first time I hooked up with him since the breakup.

So, I kno I'm being an AH, but who is a bigger AH? (not including John)