My daughter, also 11 months, has been biting for about 3 months now. At first it may have been a positioning related, now I am positive it's because I reacted poorly initially & she is hoping for a reaction from me. The first few times she did it, I yelled. Not yelled at her, but it so took me by surprise that I yelled "Ow". Now when she does it she giggles.
If it's a new thing for your granddaughter, start with checking for tips on position. I'm a 'veteran' breastfeeder, over 10 years combined nursing time but my daughter has a weak chin and I think that caused her to latch on differently than my others. Tell your daughter not try not to yell or react to it. Pushing the child in toward the breast may help as some have suggested. Having a teeth toy nearby & giving her that when she bites may help. If it's a habit now though, if she's doing it for the reaction, a very quick time out may be in order. I take my daughter off the breast, re- do my shirt & stand up (I nurse in our bed) for about 30 seconds. Also when she doesn't bite me during nursing, I sing or talk to her while stroking her head. She seems to like that enough to not look for the response she gets from biting.