I was replying to someone who had said that the game would be ruined if there were more sex animations/gifs. (I couldn't think of a word besides animation)I am unsure what you mean here, you can have sex with any charmed person.
Mom depends on the exact approach you took, and how you charmed her and Gabby, or if you did. You can fully charm her to have sex at any time, but there are other approaches not so much.
No one else has these restrictions and sex is available anytime after they are charmed., aside from say choosing to not charm Tracy as a lover and a cases for Mr Beasley, John Adams.