AITAH for dating my "best friends" ex boyfriend?

I know from the title, you're all probably going to think I'm a terrible friend for doing this. But here's the story. So about 3 years prior to this, I (23 F) met this guy, we'll call him Luke (25M) through some close friends. As soon as we met I started crushing on him. He was cute, sweet, funny and just overall a good guy. I started to crush on him so hard that I felt like I was in one of those cringy nickelodeon sitcoms. We clicked as soon as we started talking. After we met he gave me his snapchat and we started sending each other memes on a daily basis. Things were good and I could tell he started to catch feelings for me too. Then about 2 years later, somehow, he met my then best friend, we'll call her Clara (23 F). Clara was the type of girl to say she's nice and acts all innocent but then she talks crap about other people -especially other girls- behind their backs. Me and her were best friends since kindergarten but throughout our entire childhood she always had to be better than me. She would constantly put me down to make her seem superior. I remember when it was her 12th birthday party, she was talking ahit about a girl she said was her best friend literally the day before. She was very two faced an even to this day she is. Nowadays she's very sensitive about any little thing anyone does that she doesn't agree with. She holds on to way too many grudges. She's talked crap about me behind my back even before this whole thing while we were still friends. Anyways, all in all she's never really been the greatest friend. She bullies people for being even slightly different from the "average girl". It makes me sick to know that she thinks she's such a nice person when all she's done so far was hurt the people around her. Clara even got bad at her now best friend for something that wasn't even any of her business. Anyways, Clara and Luke met and within a week of them knowing each other, they started dating. But something was off about Luke while they were together. Clara has a lot of guy friends, which Luke wasn't too happy about. He kindly spoke up about how he wasn't a big fan of her having male friends. Which is understandable at the beginning of a relationship, but she went absolutely crazy when he said that. She broke up with him after about 4 months of a seemingly perfect relationship. They never fought until the break up. Which just says everything he needed to know about Clara. It showed how sensitive she was about things not going her way. Side note: She left Luke for another guy she knew for 5 days. So Luke was absolutely heartbroken he reached out to me and I listened to him. I felt bad for talking to him because I thought Clara wouldn't like that. But when school started again in September, me and Clara grew further and further away from each other. We never really talked anymore and everything she said to me sounded like she was trying to piss me off. It never worked but the fact that she was being so salty for no reason upset me. So fast-forward a few months, me and Luke had been talking more and more and I fell even deeper in love with him. So in February of last year, he asked me to be his girlfriend. Obviously, I said yes. When Clara found out about me and Luke, she went absolutely bananas and started yelling at me and blocked me on everything. Weirdly enough, she was with her boyfriend when this happened and me and her had completely stopped being friends before this so I have no idea why she was so mad. She went on to post ahit about me online. I didn't care because I knew she was just being petty. Anyways, Clara and her boyfriend are in a happy relationship and me and Luke have been together ever since that happened and we couldn't be happier. That summer was one of the best and worst summers of my life. And im grateful that all that drama is over. So AITAH for getting with my "best friends" ex boyfriend?