Perhaps, but that was outside of the game. Mike happened within the timeframe of the game, and other scenes with other people happened in flashback or Jeremy filmed it. Ivy and Mark was outside the timeframe of the game, and we don't see it in flashback either.
Ivy has probably had sex with a lot of guys in the past, but there's virtually no evidence of it in the game, compared to most of the other women. Which totally contradicts the original commenters opinion, that Ivy will jump on any dick, besides Ians.