another option is to tell her that she gets to play on one of the accounts for free =P.

when i told my girl that i was gonna start multiboxing and that i'd need her account info so i could resub on my credit card, the first thing she asked was "does that mean i can log on my hunter again ^.^"

(background story, she's a poor college student and i'm recently graduated so where i have a little extra cash each month to support this increasingly expensive habit, she was wanting to save money to buy more ramen, thus cancelling her account till next summer :P )