convince someone your pants off

It means, she is ready to fuck you if you believe her.
Used especially while you're referring to your female friend in your conversation, though it can be used by females for males. *his/her pants off* is used as an adverb in this sentence. It means, she is ready to fuck you if you believe her.

Person1: Hey mane! I heard that you were hitting on her. Is it true?
Person2: Nay, she is just trying to convince you her pants off! (convince someone your pants off)