AITA for thinking on leaving my best friend (21F) just because of a problem she is not even responsible for?

I will br straight here, we have been friend for alredy 10 years and thing havent gone too well, i confessed to her once when we were 16 and got rejected, but we left it there because we liked eachothers company and we didnt want to let this ruin our friendship.

Years go by and i have to sortoff deviate my head towards another place but keep that faith inside of me that one day i could be the one by her side, as the years went she did get a boyfriend and i absolutly supported it, he was a nice guy but after 3 years he broke up with her and sortoff dissapeared, i was left there to be with her and like the dumbass i am i went full availability for her back again, i felt that after that breakup i had a chance, at least even if it was not real i just wanted to feel what it was to be with her.

Months later i propose to her, oh suprise, she rejected me a second time, this time a bit more like... "oh look, i am not currently ready for any of these to be honest". needless to say i got fucking broken but meh, just sortoff ignored the pain and continued.

Now have in mind, she has only ever had THE ACT with his ex-boyfriend, and she always sayed to me that she wanted to think before doing it with him (she waited like 2 years for it).

Well, just like a week ago, i told a good friend of mine that i still loved her anyway, and after that we went to a hangout and she was also there so i got to present them, well i sortoff wandered to talk with other friends and they were... talking a lot to say at least. shit goes by and as we are leaving they exchange contact, all good.

All good until they start to hang out... i am not pissed by this but yeah, they go once, go twice, and i am concerned so on another hangout i grab my friend and take him to a hidden place and genuinly ask him "yo, listen i dont wanna be saying things but is there something going on between you two? you can just tell me i wont get mad" He then starts to negate with a lot of calm so i trusted his word, we were friends since kids after all.

5 days go by, i get texted by my best friend (21F), she tells me "yo, HE is a fucking dumbass" and starts to tell me about how he manipulated her onto going to his house and then setuped it in a way she couldnt refuse to do the deed with him, and i genuinly broke inside...

She met him like a fucking month prior, how the fuck do you go from: "i dont and wont fuck with anyone unless sure" to: "oh yeah ill fuck this guy" DEAR GOD, and whats worse, the fucker explicitly told her not to tell me... what the fuck do you mean. left to say i was fucking pissed with HIM, i fucking trusted his ass, he fucking knew how i felt and still did that, AND EVEN HAD THE AUDACITY TO TRY AND TELL HER NOT TO TELL ME. needless to say i got fuming and also started throwing with her, she was all like: "he is such a son of a b, i wont ever hang out with him ill, still i cant say i didnt like it, it was nice and i gave my authorization, he is not a men does bad thing r word but i dont like how he acts"

Thing is... with her i couldnt really get angry, she was somehow the victim, still i couldnt even fucking look at her in the eyes, cuz she fucking knew i still loved her, and even so she decided to do it, and tell me afterwards trying to get some comfort out of me. I know i should be the comfort for her since i always sayed to her that i will help her at anything... but i just cant fend off this feeling of betrayal, i got myself into this, and got fucking almost NTR'd except for the fact we arent really a couple.

I am honestly 80% thinking on just going away and leave her be, but i also somehow wanna stay cuz she sortoff is a victim.

AITA for being on a 80% of me just leaving her to be? i am ducking suffering from this and idk what to do.