What is the ruling on a daughter's marriage to a guardian other than her father in the marriage contract, and what is the ruling on a mother who concealed her daughter's marriage from the father and participated in a charade to seal the marriage contract?

The girl erred by proceeding with the marriage without a guardian, and the mother erred by concealing the matter from her husband. This marriage is invalid according to the more preponderant opinion. As for the contract that was performed as a pretense, it does not affect the validity of the marriage, due to the Prophet's (peace be upon him) saying: "There are three matters, serious in earnestness and serious in jest: marriage, divorce, and revocation [of divorce]." The marriage certificate is merely a documentation of it, and it can be changed with another document that includes the guardian's consent. If the man had intercourse with her in this invalid marriage, there is a difference of opinion among scholars regarding the necessity of istibra' (waiting period to ensure no pregnancy), but the more cautious approach is to observe istibra'.