Congrats on the new bunny!
Bunnies should not be eating grains or yoghurt. You should be feeding her rabbit pellets such as Science Selective pellets or Oxbow Essential pellets. As a rule of thumb rabbits should not have grains, bread, diary (milk related things) or anything that has too much sugar as it can upset their belly. Their diet should consist of unlimited hay, 15-25 grams per kg pellets and a good amount of green leaved veggies (endive, chicory, spinach, etc). (Dried) Fruits or carrots (which are high in sugar and thus should be seen as a treat) can be given once every few days and the amount equal to 1 grape or 1 cherry per bunny.
How long has she been with you? If it’s less than a week she may still be settling in and scared. Does she have a cage or pen? Make sure she has a space where she can hide away and leave her alone for at least a week (aside from feeding and cleaning ofcourse).