I think I accidentally became a surrogate parent to a kid online and I'm having a crisis about it?

DISCLAIMER: I have OCD. I might be overreacting. God I hope I am. I'm not really looking for reassurance, more for next steps (and even if I was looking for reassurance, don't give me it. It feeds my mental illness. Also it's against the rules, lol)

I'm an adult, at least 3-4 years older than this kid. We talk about fandom stuff. I see myself more as a friendly mentor and often have to interact with minors because I am in fandoms that are more kid friendly. I do not discuss NSFW topics with them WHATSOEVER. I give advice, occasionally make jokes and we talk about story stuff.

They've taken to calling me slang for a parent, now? I thought it was a joke at first but now they're doing it consistently. They don't seem obsessed with me at all, or at least I don't think they are. My question is what exactly do I do, here? Do I discourage them and tell them to knock it off? Or do I just accept this?

I don't think they have any issues with their parents at all. They haven't really said anything of that nature or measure, but they have mentioned mental health issues (which is why I'm asking for advice, so I don't hurt them somehow) which is something I want to respect. That's most of the reason I see myself as more of a mentor because I was in the same boat as them. I see a lot of my younger self in this person.

I also ended up being groomed at the same age they are now. I don't want to be like the person who groomed me. I've even given them (and other minors in a community I moderate for) advice for how to sniff out groomers and have told people if they get groomed, it's not their fault but the perpetrators. My OCD makes it hard for me to think clearly and I need to know if I'm possibly curating something unhealthy if I let them do this?

Again, they don't seem clingy. They don't desperately message me, it's just... What do I look for if this does turn obsessive? How do I let them down gently? I don't want to cut contact because I think that would destroy them. I know what it was like to be dropped like a hat at that vulnerable state and it fucked me up. I get I'm not technically responsible but I fear if I were to do that, even if it was for the 'best' I'd end up driving them to worse places or people.