(F18) boyfriends ex keeps trying to follow me?

Me and my boyfriend, both 18 have been together for about a year now. I know I'm young but I'm confident in our relationship and where it's at right now, and despite the fact we have both had our issues, we have both promised each other to work together against any problems that may come our way.

Now this doesnt really seen like an issue to me, but I have found it odd. His only ex has been trying to follow me? I have a private instagram account, only with my close friends on it, and multiple times I've gotten follow requests from her. I didnt recognize who she was at first, but saw that shes got mutual friends of mine and assumed it was someone I might have knew or met and accepted it. Not until my boyfriend told me that his ex followed him I realized that she was the ex. I removed her from my followers pretty quickly after that.

Im my boyfriends first long term relationship besides this girl who he dated I believe in the end of middle school, freshman year, whom he dated for 3 months and didnt consider to really be a significant relationship in his life and that they were pressured into dating each other, plus some other problems that he has told me about. He told me that she has a pattern of trying to follow him and he isnt really comfortable with it, I'm not comfortable with her following him either for obvious reasons, given the fact that they are exes, and I dont know why shes is possibly hung up over him if it's been 4 years since they dated. I don't think that it's impossible that maybe she just wants to reconnect and be friends again, and if be a hypocrite if I said I didnt want then to be friends at all, since there are two people I dated (short term, like 1-2 months max for both of the relationships) that are good friends of mine now that I rarely think about the time in my life where we were "dating" but he has said that about two years ago she tried getting back with him and this was before we met. Eventually she moved schools so I've never personally talked to her before besides learning that a lot of my friends are friends with her as well.

Shes seemed to have backed off, and hasn't seemed to have tried to follow my boyfriend since (at least to my knowledge) because he usually tells me when these things, but I've declined a few of her follow requests but she keeps sending follow requests? Should I accept her follow request or at least try to ask her first why she wants to follow me? I find it a bit wierd but it doesnt really bother me. But is letting her follow me a bad idea? Is this posing a risk to me and my boyfriends relationship and could this just stir the pot and should I play it safe? I dont really expect her to be trying to follow me because of our relationship, and I wouldnt think it's because she still has feelings about it (especially because it was a middle school relationship, that they dated for 3 months)and I really dont think she has bad intentions, nor do I want to assume she does because I have never met her or talked to her before, but I still want to be cautious

TLDR: ex of my boyfriend that was in a short term relationship (with mutual friends of mine) that I have never met/talked to keeps trying to follow me on instagram. Do I accept it?