First of all, make sure the shoes are drying out thoroughly. A lot of people put them in a synthetic zip-bag that just seals all the sweat & stink in there.
My feet aren't terrible, but as someone noted, this goes with the territory. I put talcum powder in my shoes before and after every practice. It absorbs sweat as well as neutralizing the smell. Switching the insoles more frequently may help (and is certainly cheaper than switching shoes so fast).
I know some people wear nylons, tights, footsies, or even socks to help absorb and/or trap the sweat so that the shoe remains relatively unaffected... and you just throw the offending layer in the washing machine to be used as a barrier another day.
I think there are sprays which are supposed to suppress sweat... she could maybe even try a regular antiperspirant.
Hope these or other idea help!