Medieval times weren't great at supply & demand vs working at swordpoint.
These are all fairly relevant to the question:
How easily can her services be forced?
What sort of kingdom is she in, socially?
Does it have any kind of legal system or concept of rights of peasants?
Can the king throw her in a cell and force her to heal his best soldiers under threat of death for her and everyone she cares about, North Korea style?
If she has no powerful friends, that could be her fate: to find herself locked up and used as a resource of the state.
On the other hand, if she either has the favor of some nobles such that she can't just disappear, or if the kingdom has some kind of trader class and a legal system that has some kind of respect for individual rights of commoners... then she could become fantastically wealthy.
Rain.... rain is worth something, particularly if she can call enough rain for thousands of square miles, but it's nothing compared to healing if she can heal serious things.
How many nobles are there within reasonable travel distance from her? Thousands? In medieval times commoners saw child mortality rates of 30-50%. Nobles weren't much better off.
A few thousand nobles will include hundreds of people with dying kids, wives facing non-trivial risk of death during childbirth, lots of people occasionally facing possible death from what would now be treatable infections and lots of elderly counts and barons facing all the horrors of old age.
If her magic can clear a chest infection from a dying child or save a prince dying from sepsis from an infected wound.... saying that she would be highly in demand puts it lightly. She would be worth her weight in gold, literally.
If she found herself attached to a noble household we'd expect to see the rich and powerful making journeys to her with sick family members, and access to her would be used as a political bargaining coin.
If magic users were more common then you'd expect it to be routine for any noble house to have a mage associated with them.
The more common you make them the lower down the social hierarchy access to mages goes.