All of my 'persons' are unique, and real people, real phone numbers and real addresses. And, each is using a unique IP address. So, even if I were to win with all of my accounts (which I know is not likely to happen), I would still not be in direct violation of the ToS. Well, except for me @work vs me @home. Most of these people were 'recruited' for Club Bing 'mules' (?) and I let them order/keep a bunch of Bing prizes (crap I didn't want, one man's trash...). From time to time I (ab)use them for other stuff, too, but since more often that not it nets them the 'secondary' prizes that I don't want, they don't mind.
So, why not just ask your girlfriend to use her phone number? Or use your home phone vs your cell. For this promo, it is highly unlikely that they will actually call the number, and if you don't plan on TXT'ing in your codes, it won't have to be a cell phone.