I can imagine how distressing this must be for you. You don't mention whether you saw her while she was ill or if you know what was wrong. Did you make an effort to see her and support her while she was in the hospital? If you ignored her, then she probably feels that you don't care about her. If you have done everything that a supportive partner would do, maybe you could ask a mutual friend or one of her relatives to try and find out what happened to make her cut you off. It might be nothing to do with you. Perhaps the medical reason for going to the hospital has made her have to reassess her life and she doesn't know how to tell you. If you love this girl, be kind, understanding and patient, and let her know gently through whatever means possible that you still care for her.