What is the ruling on a married woman speaking with a non-mahram man over the phone, while she loves him, knowing that her husband discovered the matter and forgave her twice? And is there a way for her to repent?

What you are doing by speaking with a non-mahram man is a reprehensible evil that exposes you to Allah Almighty's wrath and punishment. Fear Allah concerning your husband and preserve his sanctity. Repent to Allah with sincere repentance by abandoning the sin, resolving never to return to it, and regretting having committed it. If you repent with this sincere repentance, Allah Almighty will accept it by His mercy and overlook your misdeeds, "And He it is Who accepts repentance from His servants and pardons sins, and He knows what you do."