I think the eZee Chopper which is designed for the smaller person could just be right. The agents
Onbike are very helpful and may be able to measure the minimum saddle height for you. It has a sprung seatpost which wastes 2" and that could be changed for a normal one. It is an expensive model though, but a superb hill climber. It's maximum assist speed is 13 mph.
Otherwise, for something cheaper you may find a model amongst the various small wheel folding types. This
Battribike Buzz is about the smallest I've seen, heavy with SLA battery, but very low cost. Again the sprung seatpost can be changed to drop a couple more inches.
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