That’s all about unhealthy social comparison and obsession. It stems from insecurity.
in your situation it sounds like she’s prob being nosy or wants to see what you’re up to but if you said someone from your past randomly requested to follow you i wouldn’t think much of it. there are lots of people who i’m no longer in touch with that i’m curious about. it doesn’t have to be a negative thing always like i love to see who’s getting married or who moved to another country or who’s having babies. but maybe i’m weird but im a social butterfly in that sense
i dunno, i like reconnecting with people from my past and seeing what they are up to! i tend to think it’s innocent unless it someone you specifically had issues with.
It’s just to be nosy. I’d keep her there so she can see how well I’m doing in life now, but there’s nothing wrong with removing her either if that would ease your anxiety