actually it's better to have her work two shifts. day and night shifts. this means 14 time slots per week. you could also have like 3 girlfriends at 1 time slot per week each. and they will love having the stability of knowing no matter what happens to some of their "boyfriends" the bills will get paid by the others.
this is how women want it anyway. they like having backup boyfriends. and it is also how men want it too - they like to cheat, and don't want to have a hoe breathing down their neck 24/7. this way you get your freedom but still get to drain your balls on a regular schedule.
face it - like all my ideas this is genius.