Does informing the mother permit speaking with the girl? And is it obligatory to cut off the relationship with her immediately, or to gradually distance oneself from her? And is it possible to continue the relationship with her and end it in marriage?

Relationships that lead to adultery and immoral acts are forbidden, and must be severed immediately and repented from. Informing the mother or intending marriage does not justify continuing them. One must beware of Satan's deception, who portrays the relationship as necessary. One must strive for a legitimate marriage with the fiancée after her engagement by her family. The fiancée remains a stranger until the legal marriage contract is concluded, and it is not permissible for the suitor to speak with her except to the extent permitted by Islamic law. If marriage is not feasible, then one must separate from her.