In addition to cruiser, I'd also think about crank forward (like this Electra Townie) where it allows you to sit and be able to easily put your feet down. (7 speed costs $450, don't know what a 1 speed costs)


If she's worried about balancing, think trike (Worksman trikes start at $370).



And, for what it's worth, lower gears (but not more gears) can help with the wind (you won't go any faster, but you might get less tired) - just like hills.