My ex’s ex keeps adding me!

I was with my ex for like 5 years on and off. And that was 4-5 years ago... The last time we were together we ended things on a good note and we’re just friends for a little bit after we’d only talk here and there but we had no feelings for each other and started seeing other people. Which is when he met this girl. Well one night he went out with this girl and a couple friends including my best friend and she went off on this girl how I’m the only girl he’d ever love and whatever. She was just drunk and she’s just use to us being together and has been through everything him and I went through. But I was completely over him. So anyways him and this girl broke up months after that happened. And a few months after that she added me on Facebook&instagram.; I denied it. So now it’s been like 3 years since they’ve been together&I; have and don’t want anything to do with him(he’s on hard drugs and just crazy I hear and in prison now) so months go she added me on Facebook. I thought it was weird and I just ignored it. Well a few weeks ago she added me on Facebook again with a new Facebook and today she added me on Instagram.. like wtf! I have nothing to do with this girl, I don’t even know her I just know of her. Nor have anything to do with my ex obviously. Why does she keep adding me on stuff?!