Just checked my recent stats vs Mom, 1 lose in 27 games. I use a 3 warrior build, so pretty much the same as Mom, and yet she has far superior cards to me. Given this it may be time to start either getting another even higher bad guy, trying to improve the AI a lot more or give her even harder cards.
Gang up on the human, he has very little block and very few ways of getting away from you Do not gang up on the elf unless you can get a player each side and attack from the rear each turn. You need to take him down in 3 hits or less or you will struggle. Far safer to attack with a single player when you see the elf with only a few cards. Just keep away from the dwarf until you are ready, he has very little movement Hog the vp's, Mom will forget them if you put a player within reach for her to move to, allowing you to run your own player in It might help that the crypt levels really aren't mom friendly.