Wow! I feel like I just read a novel! (claps)
Anyway, it sounds like Joe's step mother a complete bitch, yet she's dependant upon him because she has been spoiled already. She's adapted her mental capacity to always get things the way she wants it, even if it means manipulating others to do so. She should see a psychiatrist.
As for you and Joe, that sounds great. I really hope it works out for ya both