My (29F) girlfriend still sleeps with her mum. Should I (28M) be weirded out?

Me (28M) and my girlfriend (29F) have been dating for over 6 months. We don't live together. She lives with roommates but they are all out of town so the house is empty this weekend. Her mum is visiting this weekend.

I'm going to meet her mum for the first time on Saturday for dinner. I asked my gf if I could sleep over after that. She said yes, but I'd have to sleep on one of the empty rooms, because she wants to sleep with her mum.

She has said in the past that she loves sleeping with her, and that sometimes, when she goes home and visits her parents, she sleeps with her mum and her dad has to move to a separate room.

I'm a bit weirded out by this. Should I be?