Is this behavior of my girlfriend normal?

Hi, my girlfriend goes to sleep at 8/9 PM everyday and it's driving me crazy. She sleeps until 9AM. We have been together for 5 months now. The first 2/3 weeks of the relationship she was going to bed at 11/12PM. We see each other only on weekends because of my work. The weird thing is that we can not talk that much for the entire day and she still won't stay a bit longer to talk or when we talk and 9PM rolls around she goes to sleep, period. Is this behavior normal or is she texting someone else?
Is this behavior of my girlfriend normal?
Post Opinion