Sure, they'd rather not have their teeth brushed. Start with just rubbing the back of the brush against her mouth, if she objects, just go that far and stop. Do that a few days, until she doesn't mind it too much. Then try lifting her lip and laying the brush against her teeth. Don't move it, just lay it there every day until she doesn't object. You see where this is going, doncha? Do just one little non-threatening move at a time until she's okay with it, then move on to the next one. Pretty soon she will be allowing you to brush. It doesn't take much brushing, more of a wiping. They especially don't like having the front teeth done so leave them until you're both comfortable with brushing.
