Will there ever be an episode where she has a major role and is more active than usual? Usually she's just in the background.
Does Trey Stone and Matt Parker(joke) have any intentions of developing her?
Why would they? Pretty sure she only exists to mock an ex-girlfriend one of them never got over. If she develops, that implies she is or was ever meant to be more than that.
Plus when does a character besides Kenny and Mr. Garrison develop on this show?
I'd give her a smooch.
Her entire existence was because Trey's ex-fiance cheated on him, and he took years to get over it. Now, Cartman's mom is just kind of there since Trey's married now.