Why not just make it 24 hours again. I doubt that many gals will change their opinion about someone within those 24h. Everyone will take actives even if their score isn't very good (I think), unactives get exiled anyway. Like in my gal, there are two PA-active players (*) but they don't respond to ANYTHING, so they're completely useless. I would like to exile that kind of people sooner as well.
I haven't yet had a spy of this sort, but shortening it to 24 hours should minimize damage