Like what mruffruff said,, have your brother feed her etc,,, also,,, talking to her quietly and maybe get down on the floor with her,,, maybe not necessarily to try to coax her to him,, but to just sit quietly near her and let her come to him on her own,,, maybe if he is closer to her ,, he wont seem so imposing.,,,,,

Best of luck.... Trust is often a hard thing to earn with a dog,, but when you get it,, you got it!