Mine always has new people liking her posts, but they never stick around long.
Yes, I noticed that about my ex as well. I even went back through a year's worth of her FB feed to analyze this. The group of people interacting with her a year ago are COMPLETELY different than currently.* Her IG posts are the same way. Sad.
*This is especially hard to explain, considering Facebook's algorithm tracks friend interaction and intentionally shows your posts only to those friends that have interacted the most previously. For this phenomenon to be explained, she would've needed to have done a lot of adding and subtracting of FB friends throughout the year, totally unbeknownst to me.
There are a few names that are the same, but I've discovered that many of these are high school friends, and she never sees them. Her Facebook is private, but I was friends with her for six days recently and went back and looked through her timeline. A lot of people seem to disappear after a while. Some reappear after several months. She's friends with at least three exes, and I am pretty sure one of them is one who supposedly abused her.
One thing I've noticed is that she NEVER refers to anyone by name. It's always, "The guy I was seeing at the time" or "My best friend from college" or "My one friend." I think it's because she pushes them away and then pulls them back in and doesn't want anyone to realize that she keeps doing it. I think this is also why she rarely says anything negative about anyone on Facebook.