It's not necessary to avoid cheating, it's just harder and needs a certain strategy --- you can date all at once if you learn which date locations are watched by each. The park is watched by Valeria, the cinema is watched by Galina , and the restaurant is watched by Milana. Don't go to any of those locations with a girl who isn't that location's watcher. And you can romance Anna with anyone as she doesn't have a reaction for cheating.
If you don't radicallize all of them by the end of the game (w/ successful revolution), 1 or all of them may die.