She is latching incorrectly. I breastfed my youngest until she was 3! My middle until she was 1.5. I didn't have any problems with teeth during this time. In biblical times, it was up to age 3! That was when they weaned the child. Occasionally you may get bitten, however, when they do, take the breast away immediately, and show your dismay. Say to Maggie, No, don't bite Mommy. Breastfeeding is something between Mommy and Baby. No one can give you advice on how often, or how long to feed. Do what you think is right. I hope she is on some solid foods as well.
If she is biting you, take the breast away, and try to latch on again. Say ow, and explain that it hurts mommy, don't bite, don't use teeth to drink.