Dating a mommas boy

Long story short. She makes inappropriate comments (saying I have big books, and he has 'grown' downstairs etc)

He said that if she doesn't want us to be together than that isn't his choice and that's that. She accuses me of giving him drugs because he has hayfever or is tired??

Not only to him tho, she talks to all of us (me him and both his sister (ages 10 and 8)) about her sex life and stuff. He blamed all the lying he did to this relationship on not spending enough time with his mum. What do I do???