Something like this is not impossible, but this is a pretty far fetched situation (like, for example. why this hypothetical woman would remember a past hook up and conclude that her husband is not good enough. That doesn’t make sense). Literally everything that comes afterwards sounds like it comes from a melodramatic soap opera that is divorced from reality. Have there been people who hooked up from past lovers before? Yes. Does a purity culture (like the one we have) stop infidelity? No. Infidelity happens regardless of whatever cultural set up there is. Two single youngsters hooking up for a while and then going on their separate ways is not necessarily going to lead up to some melodramatic soap opera situation later on.