here are some things to try that may help. your snake may be getting afraid be of you standing there watching, dim all the lights in the room (so you can still keep an eye on the mouse) and just leave them be for a while making little movement. Do you move stuff around in the enclosure before you feed or do you just drop the mouse in? Sometimes, bps like to 'hunt' from the safty of a hide and set an ambush for their prey. just keep trying...these kinda things happen sometimes. Just keep a watch on her weight to make sure she is not loosing too much.