Help me

My 19 month old has been waking up from 1am to 4:30am every night for the past week. She cries bloody murder until she’s gagging and almost throwing up. When I go into her room she immediately wants out if the crib and wants to play. She will NOT go back to sleep until 4:30am. I’m beside myself. I have no idea what to do. I’m exhausted and have a full time job. Please help. Does anyone know what’s going on or have any suggestions? Please, I’m desperate.