I'll use English to make it easier for your friends, since using Chinese to talk about US patent process will only confuse everyone.
1. provisional patent application vs. patent application
A patent application is not a patent. When file a patent application, the filing date IS the invention date, so the quicker you file an application, the better chance you beat out everyone else to get the patent.
But patent application is a legal application, it takes time to talk to a lawyer and draft the patent application, and while that time, someone else might file for the same invention.
For this reason, US law allows provisional patent application. A provisional patent application t (1) shows you invented something, using lab notes, emails anything that can prove you have the invention (2) filed to USPTO to reserve the invention date as of the date of filing. Within one year of filing of provisional patent, you can work with a lawyer to submit real patent application.
In your case, one year ago, C contacted hospital lawyer to submitted a provisional patent application. Now one year later, it is time to file a formal patent application with inventor signatures, formal drawings, formal legal claims etc.
2. What your friend can do legally
You can let the lawyer know about the dispute. The lawyer works for the hospital, not C, their job is to get a good patent, incl. correct ownership.
If there is a dispute of inventorship, now is NOT the time to sue over it. Why? because you don't have a patent yet. During application process your application will be modified to narrow the claims. A co-inventor's contribution might be added or removed from the final patent, depend on how noval the contribution is. So without an issued patent, there is no meaning talking about who is the real inventor, because the invention has not been legally determined.
That is why I am saying, work on the application, get the patent issued by the USPTO.
