If we're serious for a moment, Mia is honestly absolutely gorgeous and I doubt there are many guys that would shove her off the bed. And that's even before you factor in her undying loyalty to MC.
But she also plays the role of his guilty conscience, and she plays it incredibly well. Never really bitching around or confronting him. Just giving MC these looks of silent disapproval, letting his own mind fill in the blanks. Basically a very hands-off attempt at cockblocking.
It's a really difficult character to include in a power fantasy like an AVN and I'm not sure yet if it was a good idea at all.