My wife is nursing. She was however advised by the doctor to stop for a few days because the baby is yellow however she need to pump so as not to lose her milk, is she allowed to pump on shabat

She should use a hand pump and have the milk come out so that it is not usable- either by putting soap or soil in the pump or on herself so that the milk becomes soapy or soiled (Shemirat Shabbat KeHilchata 36 20)