Transfer of Ownership (California)

My mother and I are co-owners of a house in which I am the only person on the loan. Recently she transferred her half of the property to my sister without my permission nor any acknowledgement of mine. That transfer Deed was already recorded with the county. Is this legal? Can it be done?

Thank you in advance.

You didn't post the state, so I'll just give you the common law.

Unless the property is owned by a husband and wife as a tenancy by the entirety, a co-owner may convey his share of property without the permission of the other co-owner.

I think state is referenced in title of post (California)