don't feel guilty! nothing is worst than being a freeloading bitch...
besides, why are you trying to find a nice way of saying this - haven't you been too nice all this time???
I wouldn't take advantage of my co-worker like she did but if I ever did, I'd rather hear him say straight up, "If you want me to keep dropping you off, you're gonna have to put in some money for gas."
just stand up for yourself and dont beat around the bush....
girls like her make all of us girls look really bad... hmp!