Just parroting what some other people said, if this is something her boyfriend is in the dark about it isn't necessarily a good thing.
I had it happen to me, my girlfriend was into a bunch of RP chat rooms (back when MSN ran a bunch of random user created chatrooms) and I wasn't super into it, but I'd show interest and listen to her talk about this or that person etc. It was her thing like videogames were mine.
But I decided to give it a try so we could spend more time together and I could get to know her online friends like she knew my real life ones.
I get into the chat and I'm like hey guys I'm 'Y' 's boyfriend, what's up. Instantly kicked. I was like uhh wtf? Went back into the chat kicked again, get an angry message from the guy who kicked me and he was like "f*cked up joke, I'm her boyfriend, don't come back loser".
When I saw her in class I was like uhh hey what's up and I explained the situation and demanded an explanation. And she was all like oh it is just an RP thing it isn't serious, the guy was just acting out his character.
Personally I didn't believe it, went back into the chat a few days later when she wasn't on. Private messaged and told her I was her boyfriend in real life and asked him if it was just an RP thing or if he thought it was real. He thought it was real. Confronted the g/f she said she would break it off. Like 3 months later, she went to a wedding came back said she met the guy, got drunk, and had sex with him and said she was sorry but it felt right.
I was absolutely floored since in the almost 2 years we went out we never did more than kiss. Needless to say I did not speak a word to her the next 2 years in school and never saw her face again after we graduated.