if you just got her she might be nervous from the environment change still. I would try putting a towel over the sides of the cage so she can't see people when they walk by. Might calm her down some.

My BP came from a similar background and has never missed a meal, even when in shed. I wonder if it is possible that after being under-fed while they mature they learn not to take their food for granted and are less likely to be picky eaters?