Why would she add me on Facebook

I woke up this morning to a friend request on Facebook from a girl. I didn’t recognize the name, so I clicked the profile to see who it was.

I saw that she is with my ex and it looks like they are engaged.

Why on earth would she add me ? Was she creeping and accidentally added me? Did she want me to see that they are engaged? I really don’t care because I’ve been in a relationship for over 2 years now and I don’t care about him anymore lol

I just think it’s the weirdest thing. I blocked her. I don’t know if that was immature or not. But I just don’t want to deal with whatever nonsense they want to bring into my life.