In a situation like that....sometimes you have to give the dumb guy a little rope and let him hang himself.
Cheat or not, Ivana still wanted Donald. But she went about it the wrong way.
In Aspen, it was clear Marla showed up to bait Ivana. Ivana fell right into her trap.
BTW, Marla was long gone by the time Melania appeared.
“..But she went about it the wrong way. ..”
It was DONALD who went the wrong way - he cheated on his wife, and the mother of his children.