You need to take your friend aside, tell him how much you enjoy his company, but that you guys are there to get your degrees, and his girlfriend is distracting, annoying, a nuisance, and...oh yeah...not on the lease!
If he doesn't have her out in say...three days, you will ask the landlord to evict her, or both of them, if he prefers.
It sucks when friends take advantage of you.
They will, and not even realize it though.
Good luck on your education!
~Christina
p.s. come to think of it, this *may* be an education in and of itself!!![]()

