my really toxic friend got with my ex of 3 years and still denies it to this day. AITAH for confronting her?

(my best friend- C // ex- Z)

context: so my best friend (C) knows all the history and everything that happened between me and Z, i wont go into detail. they became friends last year october while me and Z were still dating. i didnt have a problem with it until C started telling Z things that were between me and her only, and she sent me like a screen recording scrolling through their chats (really fast, so messages werent really visible) to show me how much theyve spoken like okay? (keep in mind we were still together at this point.) and in that screen recording i saw him telling her he liked another girl?? and i didnt say anything about it i just was dry with him until he got the message. i was telling my uncle about it, (we're close in age, and apparently hes friends with Z) and my uncle told Z that i told him and it was a huge thing and i was accused of trying to "ruin their friendship" (Z & C's friendship). after that Z and i broke up fast forward to now recently this year, theyre still close. he comments things like "PRETTY GIRLLLL" on her posts, reposts her videos that she posts of herself. i was going through C's reposts on tt and theres a lot of things about a specific boy and normally she wouldve told me about it. anyways i forgot about it until i saw Z's repost that was soooo so clearly about C. just ONE thing was, she reposted something about pink lilies being her fav flower, and he reposted something that said "her favourite flower btw" and guess what? pink lilies. (there is way more proof so please dont come for me and say im jumping to conclusions). so whatever i left it even though it really bothered me because a while ago C's other friend (we'll call her S) started dating the boy C liked and they stopped being friends over it, and she went on and on and on about how she was such a bad person for doing that, and now shes done the exact same thing? its been a few days since i've known and each day there was just more proof. earlier today i confronted her about it. i cant attach images but heres our exact conversation.

me: hey girl, just wanted to ask u when u were planning on telling me that u done the exact same thing that u were calling (S) such a bad friend for? its chilled tho, just hope u know the double standard

C: bro what? is this abt (Z)?

me: yes and im not dumb so please dont deny it

C: i know what your thinking, and no we’re not.

me: its kinda obvious but okay

C: how?

i sent her screenshots of reposts, comments, & other proof.

C: we are not dating bro, i swear on my life, it’s not even like that, he complimented me, and my reply is an inside joke i have for him

me: those arent things you say to just a friend. i dont believe you (C), its genuinely just whats expected, and theres way too many reasons not to believe that you guys arent dating

C: i’m sorry if you feel that way, but i can promise you that we’re not dating, and we never intended for it to look like we are

me: just a question, if i were to be this close and talk to (her ex) or (boy she liked) like this, and we reposted things like this about each other, wouldnt it be the end of the world? and would you not think we're dating too?

C: i would’ve just asked if you were dating them, i wouldn’t have jumped to conclusions

me: theres enough reasons to come to that conclusion, thats why i didnt have to ask. if you showed anyone the screenshots i sent you, theyd one hundred percent think the same thing. you knew the history between us, and you still went and got this close to him, dating or not. and you know i never wouldve done that if it were you

C: yeah i understand that, and i’m sorry. but are we all ignoring the fact that you confessed to (not important guy) and stuff a few days after i just confessed, then still asking am i over him, like obviously not i mean i just confessed like 2 days ago.
but again i’m sorry (my name)

(guys SHE said i should tell him i liked him, and this was 3 years ago btw, we were kids)

me: that was 3 years ago (C). we were both kids, but dont make this about me to deflect off of the actual situation. theres a huge difference between us 3 years ago and us now and right now, i wouldnt have gotten that close to someone i KNEW very well you had history with

C: yeah i get that but i’m sorry (my name)

me: its chilled

C: hope ur new year is going well

it ended there but i know her well, and i can tell when she changes the topic when she has no argument or no point. i feel bad for confronting her and i feel like i should apologise or like its my fault? let me know AITAH????