It really depends on the rabbit. Some people don't give any pellets or only give a couple teaspoons a day. These people treat pellets more of a vitamin and mineral supplement than a dietary staple.
I would give a small amount, like 1 tablespoon, twice a day and see how she does. If she is fine with it over a few days, you can increase the amount by a little bit until you reach the amount where she starts to have some issues.
Many pet owners limit the pellets based on body weight. My 2 smaller rabbits get 1/4 cup per day while my larger ones get 1/2 cup per day. Some people only give 1/8 of a cup to smaller rabbits or ones who have issues with larger amounts.
The type and brand can make a difference. The pellet you are feeding might be too high in protein, fat or sugar for her. You could try a pellet with a bit less protein and fat. A timothy hay based pellet with 14-15% protein might work. You might have to try some different brands to find the one that works really well.