Any one that uses Steam / is a gamer HELP

Ok so basically my bf and I were playing a game on his laptop, and I noticed that whenever one of the people on his friends list plays a game he will get this little pop up on the right bottom corner of the screen. well he got one of those and it was his ex!! is that a big deal to be friends on Steam with your ex still?? he doesn’t know I know her full name so I can’t even say anything. I don’t think they talk anymore but idk am I overreacting??