It's true. Despite what we were told in cartoons and movies, the unpleasant people seem to prosper and everyone else just lets them do what they want.
I don't see how having a large age-gap can be immoral, unless there is a suggestion that the woman is uncapable of making her own decisions or is being coerced in some way. The downside is mainly that the guy is going to die years before the woman. If she's OK with that, and OK with his age and appearance, then there isn't much else to think about. (Most women who outlive their spouse are actually OK with it, unlike men.)
I would say generally yes, but her parents should probably be OK with it.