Do you guys live in the U.S.? The first thing to do would be get her those things. If she’s worked before she qualifies for SSDI and if she hasn’t worked she can apply for SSI. The father can go with her into the Social Security office. When you’re eligible for those things you often qualify for Medicaid and Medicare too.
Your friend can go to courthouse and get apply temporary guardianship for his daughter. This can enable him to apply for benifits for her without her being involved. This is such a common issue with people with SZ which is why many go homeless. They can be their own worst enemy. Sadly