Easy! Explain to her that with the money you'd be saving by NOT RHPing your cages, you'll be able to put more towards something you can do together - i.e. a vacay (even a weekender), a big event (what are her interests?), etc.

That's where it comes down to the give-and-take. You just have to follow through & do it! The more you make an effort to balance relationship stuff with herp stuff, the more herp stuff you should be able to do (from someone who has been involved w/non-herpers & had to make those concessions, too).