If the machine smells bad and it's being properly maintained between cycles, then something could be wrong with the machine (not draining all the water, partially clogged with some gunk, including undissolved detergent). If the machine is not being cleaned at all and the smell comes on strong within only a day, there could be something wrong with the water. Machines also shouldn't leak under any circumstances.

With any front loader it's important to wipe down the rubber door seal when you're done your laundry for the day. The door should also be left open/ajar for at least a day or two after your last cycle to give it a chance to properly dry out.

Mildew and/or mold or that type of smell shouldn't appear in a single day if the machine was clean or free of those contaminants the day before. Does your mom's water have an unusually high amount of dissolved organics in it? Has she had the water tested? Is the detergent rinsing completely out of the clothes and machine? What kind/brand of detergent is she using?

Also many machines are not suitable for use with chlorine bleach and go so far as to warn against it in their manuals. You shouldn't need to take any extreme measures to keep the machine odor free. You might want to take a read over at the laundry forum on Gardenweb as they're the biggest appliance forum on the net that I know of - and especially because people are REALLY into this type of thing.