I feel paranoid and distrustful towards a close friend

I have a long-distance friend that I've known for a few years now and have been close with. During the last few months they've been getting stalked and manipulated by someone on discord who has gone as far as publicly posting revenge porn and threatening to move to their hometown to get closer to them for something as simple as ignoring them for a few hours. Despite all the abuse and vile shit this guy did, My friend kept on going back to him for some reason to see if they "changed" until I recently convinced them to block him once and for all.
However, I'm still suspicious that they went back to being in contact with this guy, and the thought of it makes me feel hurt, upset, and most of all worried for them.
I'm worried about bringing it up to them since I ask them about it not too long ago, and they said that they feel more at peace when it's not on their mind. I feel like bringing it up again would be a mistake because

1. I believe it would make me come off as paranoid and controlling, especially if my suspicions aren't correct.
2. I don't want to potentially bring back any bad memories that involve this guy.

I care a great deal about this friend and it really hurt to see them in such turmoil when they were going through all this. Am I overthinking all this?