How can a 18 year old girl legally leave her home?

The thing is she can leave her parents along with her educational certificate, which shows that she became major and join in working women's hostel for three more years till you are eligible to get married.  If she leaves her parents and join you right now, her parents file criminal case against you and your parents, and police will harass you and your family.  Even her date of brith certificate and her statement that she volunatarily abandoned her parents won't convince the police and they will have fun time and grab a few thousand bucks by harassing you and your parents, till the matter reaches court and court will find time to look into the matter leisurely and come to conclusion that she is a mjor and she has not been kidnapped.