Well, Monica hates sex, she had it with her (former) husband 4-5 times. For Monica only her business was important, more than anything else. She had her first orgasm at the casting scene with Biff and Melanie, when she was forced to use that dildo. The second one was in the basement with Steve. She still hates people around her, they are worthless idiots in her eyes. But, something slowely changes in her subconsciousness. She doesn't realise that for now, though it's there. So, Monica will still be the same after all, but she tries to manage her situation. A hint for example is that she uses another name in the slums, talking herself into the "fact" that she can do these disgusting things because these things does another person, not Monica Buckfett. It's a kind of problem solving for her very own psyche.
Exactly this is very important for DecentMonkey. He doesn't only want to do a h-game with hot scenes. He attaches great importance on Monica's feelings, her Ego and how she reacts to certain situations. That's why you can find so much info about Monica when clickling on different items in the house. They give a lot of hints about Monica. Where she lived before she moved to the city, what she likes and hates ...
So, all in all, the MC is quite unique after all, she isn't the typical girl which get's corrupted and falls into it. Monica tries to solve her problems and does (nearly) everything to get her former live back. That's her only motivation.