Should I accept?

I had a friend of 6 years and about 2/3 years ago we had a falling out and honestly haven’t spoken a word to each other since. We’ll recently it’s been found out that she’s dating my boyfriends best friend, friend and she’s dating him. Idk confusing af 😂 and her dad recently just killed himself and in the past when he would try she always leaned on me for support and to pretty much help her get through a hard ass time. We’ll she friend requested me on insta and I feel so wired about it but I wanna she what she has to say IF she even says anything. And like why tf does she wanna be friends on social media with me like she burned that bridge real good fuckin poured gasoline all over it and lit it with a flamethrower so it’s just hella weird that she’d be the one to make the first move. Idk any advice?

It was over one of my friends at the time that she didn’t like or approve of and I was being an immature 15 year old and not treating her the best either. Thank you all tho cause though the falling out was bad I feel as if we’ve both grown and simple follow request won’t be super detrimental. I’ve recently been losing all my friends to so maybe this is a sign from the universe that I won’t be completely friendless or something. Idk I get a weird feeling from it but also I don’t, I think I’m gonna accept it and see what happens from there.