Hallucinating. Told me "is that his dad?

My sister is 20 years old. we come from a happy family she has been dating a guy for 6 years and a couple days ago he asked for her hand and she came home super excited and happy telling me about it. The next day she started hallucinating. She would say stuff that are not real or did not happen. Like she would say "did he come?" "did he talk to my mom" "my boyfriends father payed my dads debts" and the one that shook me ... I took her to a therapist and they talked and after we're out of the hospital she told me "is that his dad? he was so comfortable to talk to I really loved him" I'm really concerned. she didnt sleep for three days straight and havent been eating at all. I forced her after the doctor and after waking up she was still hallucinating. Im freaked out and don't know what to do. The doctor said it's anxiety but it seems more than that. I checked her phone to see if something happened. Her and her boyfrjend are talking normally and sweetly so nothing really happened.