Such a weird weird situation

Basically. Talking to this girl for a while now like a few months. We least 2 weeks ago and had a great time kissed and all was good. We're both in the middle of our final year at school and exams are fast approaching. When she was with me she told
Me about this guy she met at a cafe or something and asked for her number. She said no and he put his phone out and she eventually did. She's 18 and he's 23 and said he texts her often. Didn't think much of it cos she was with me and we're having such a great time. Saw a thread today saying is he too old for me and didn't say anything about a situation just asking if 23 was too old for an 18 year old and talking about how amazing he was and how everyone says that's he's too old and I'm worried that she posted it. We've never talked about the student room or the guy since but have bet spoken in a few days. Am I being paranoid? There's 2 million people on this and it's as if I know it's her but have no proof. Someone help?