Cherry's cam isn't required for anything. Lola's cam gives out no diamond rewards, but is needed for a girl. Sanshi's cam gives out rewards right now, and has a really WTF story.
I finished Lola over 2 months ago and didn't spend any diamonds. You just got to do a reset or two every day, which becomes a pain in the butt when you have to get to room 4 just to reset, which takes an hour and a half.