Former best friend is back?

So. I'm trying to gather my thoughts and feelings and I thought writing them out might help.

Four years ago my best friend ghosted me for the last time. Like blocked on social media, phone number changed, the works. Her reason why? I tried to help her get away from her emotionally and physically abusive, drug addict boyfriend. He beat her in front of their baby, and she called me to come rescue them from him. I did. She went back home with him later that night. All I said was that I didn't agree with her decision to stay with him, but that I'll always be there for her if she ever needs me. Next day I was ghosted.

I lost my best friend literally over night. And it seriously took me years to get over it and not think about her every day. Four years later, I'm married, birthed a second son, and finally just started putting myself out there to connect with other women. And I found a super rad chick with kids like mine (autistic), and we have alot in common and enjoy having our little mom dates. We talk almost daily, and I'm happy to finally have a friend apart from my husband. I've always been so introverted and shy, so making friends hasn't always been my strong suit.

After how things went down with my former friend, I closed myself off from making friends. Thinking the heartache wasn't worth my time. So making my new friend is HUGE for me.

But then out of nowhere today, my former friend sent me a friend request on Facebook. And I was honestly floored when I saw it. With a new profile, new married name, and two more kids to boast, I was shocked. Happy to see she finally got away from her ex, but also angry that it took her four fucking years to reach back out to me. We were insanely close, and from the looks of her profile, she's been good for awhile. So I'm just overall angry and disappointed that a friendship that meant so much to me, meant so little to her. I don't know why she bothered adding me now after all this time. It just doesn't make sense, and part of me wants to know why. But the other part doesn't give a fuck and just wants to keep moving on with my life. I accepted her request as soon as I saw it, but after going through her page, I'm more inclined to not bother speaking and just delete her. I don't want to even risk getting that hurt again. And I sure as hell don't trust her. I know she probably went through alot, but so did I. I didn't deserve to be treated like that. So I don't think I owe her anything now.