Any tips on putting baby back to sleep

Aleson

For 4 consecutive nights now, my 4 month old baby wakes up like around 4 or 5 am. Shes fully alert and wanting to play for about 2 hours. Before, I just breastfeed her and she goes back to sleep. She goes to bed at around 7:30-20:30. Any idea what causes this and any tips on how to put her back to sleep? Thanks