Sitting up is fun

Tara is definitely growing up. Her new thing is sitting up. When she's laying on the floor on her back she sits up. Which is fine. But she also does this in her crib. So if I put her down for a nap she just sits up crying. The same thing when she goes to bed at night. I think last night she was so tired that she fell right to sleep. The night before she sat up for 30 minutes. I'm hoping this will pass soon. I'm not really sure if there's anything I can do to get her to stay laying down. I'm open for any suggestions. It's day #3 for this.