We take turns with ds brushing his teeth ("good job using your toothbrush - now it's Mommy's turn to brush your teeth"). He mostly likes to suck on the toothbrush, too, but once he discovered how to "scrub" his teeth, we're gradually seeing less sucking and more actual brushing from him. But to get the job done, we let him start and finish, then take turns with him until we get it done properly.
We haven't yet tried this, but maybe you could also get some books about brushing teeth and see if that helps her - it seems like she's gotten soured on the process somewhere along the lines. There's bound to be some out there - there are books about everything for kids these days. It will take time, though - let us know how it goes!