ABANDONED. Girl is payment for spell/learns witchcraft

[Rossana]

I read this novel one, maximum 2 years ago- I believe it was recently written, as the second novel in the series was not out yet. It is set in modern times, part of a series- possibly YA?
Girl lives with her single mother ( who is a nurse?), they are poor. The mother brings her to a witch as payment for a spell that the witch did years ago. This witch always claims as payment for her spells something that is very dear to the beneficiary ( the girl sees this as cruelty).
The witch is sick and dying and wants to teach the girl her magic so the girl can be the next in line. Girl is forced to live with the witch in the same house.
There is also a son/nephew of the witch, but he either doesn't have magical powers/ cannot inherit because he's a boy (cannot remember). He lives close by but not in the same house. The heroine and him become involved.
I think there is a reveal at some point whereby the dying witch is actually the girl's real mother but may be mixing this with another book.
Thanks!

[Lobstergirl, au gratin]

Rossana, are you still looking for this or did you find it?

[Rossana]

Still looking but a bit hopeless by now.

[Bargle]

No where near hopeless. Our current record is 8 years. Just keeping bumping it every month or so and chances are it will get answered.

[Lobstergirl, au gratin]

How about now?

[Lobstergirl, au gratin]

No response, moving to Abandoned.