Gosh, I forgot about this thread - glad I'm only a couple of days behind seeing this.
To be honest it sounds almost like they have an eastern kingsnake, which are known for getting pretty stuck on reptiles/being hard to switch over - wait no, you said cali, sorry. All I can really suggest is the common stuff. Scent the mouse with tuna/fishy catfood or rubbing a dead anole all over it, putting the snake and its meal in a cup/lid (with air holes) or paper bag in side the viv and leaving it overnight, and making sure you start out with it warm enough. Skip a meal if it's a good weight, maybe. I haven't had many feeding issues with my guy, either. He preferred to be drop fed his pinkies when he was on those, and he refused his first hopper, but otherwise he's a garbage disposal.