Non-ethanol gasoline will help, but won't alleviate all of the issues with the gas. The problem with ethanol based gasoline is that it absorbs water. When it sits long enough, the water in the gas will start to corrode the gas tank. It will also start to create solids in the gas, which can clog fuel filters and damage fuel pumps and possibly even the injectors. You'll get varnish build up.
Your Mom's best bet is to use a fuel stabilizer in the fuel, such as Sta-Bil. This will help prevent the gas from going stale. Gas, whether ethanol or non-ethanol, will only be good for about a month without the stabilizer. With the stabilizer, depending on the amount used, will be good from one to two years.
As an aside, the main thing your Mom really needs to worry about are seals which may dry out. She needs to drive the vehicle at least once a month. When she drives it, it needs to be completely and thoroughly warmed up. A 10 mile drive should do what needs to be done.