My wife can‘t use dual hand brakes. Any kind of suspension system would be welcome as well.
Several of this company's bikes have the speeds and coaster brake you're seeking. The Townies and Cruisers specifically. I noticed that they have ladies varieties as well. (As well they should, said Capt. Obvious)
Look for any bike equipped with Shimano Nexus. Most have as many as 7 gears and can be equipped with a coaster brake. Another brand that offers as many as 9 gears is SRAM. Their i-Motion setup is probably the best in the business besides German-made Rohloff. Failing that, you can have an internal gear hub with brake laced into almost any wheel. but it will be on the expensive side. If the bike you choose to retrofit has derailleur gears it will probably be necessary to have a chain idler installed to take up chain slack. Keep in mind that suspension on a bike is for the same reason there is suspension on a car- not for comfort, but to keep the wheels on the ground for better handling. On top of that, suspension will absorb energy, so instead of your pedalling efforts being transferred to the ground to go forward, a portion of it will be dissipated in the suspension.
