Ok so here's the rundown I (15F) had a best friend (16F ill call her Leilah) for 12 years. My other friend (I've known for 10 years and we are still best friends her name is Alisa) tells me that Leilah is shit talking behind my back to her (pardon my french) and I've had her say things to my face during arguments and we got into them very frequently. I knew her email password but decided not to snoop for a while because I didn't want to be what she said I am. My friend Alisa did tell me the kind of stuff she said behind my back (calling me ugly, a bitch, annoying, a pick me, etc.) but despite my urge to check I didn't. One day she told me to check her email because her computer broke so I did. I think you know what happened but if you don't here we go. I check her email and once I text her the grade she got I got tempted and looked through her messages and took some screenshots for later blackmail but I did find the stuff i thought i would. One day she was shipping me and this other kid in a group chat (the other kid had a crush on me) and I eventually told her to F off because it was getting on my nerves and i don't like him like that (i deleted that chat because i didn't wanna reject him rudely) and then we got into a huge argument and i sent the screenshots i took for blackmail and she called me an ass for it so AITA?

EDIT: Btw i snooped in the first place because Alisa had lied about leilah saying things before but soon i saw exactly what i knew i would and i hoped i wouldnt and took a screenshot of it which i understand i shouldnt have also by blackmail i dont mean like ill make her do stuff or im gonna share the photos, i meant like eventually gathering enough info so when she says something "bad" i apparently did (i never did anything truly bad) and dump this on her