I've noticed that some manufacturers only offer step through frames in one size. That might be a problem if the one size is too big.

IMO (having tried it) a suspension fork is a bad idea. A suspension fork makes it hard to mount things like a front basket. It's less expensive for the manufacturer to build a sturdy bike with a rigid fork, and you just aren't going to get real use out of suspension even on a dirt road or gravel path. Fat tires will help a lot more than suspension.

A drop bar isn't necessary but it can be more comfortable. A flat bar tends to put your hands in a position that will aggravate things like carpal tunnel syndrome, and it can cause new and exciting hand problems. Drop bars let the rider use a neutral wrist position. There are other bars (like cruiser bars, mustache bars and bullhorns) that can give neutral wrist positions. It's not a big deal for short distances, and some people are happiest on a flat bar.

There's a lot of YMMV in terms of what's the best bike. It's pretty common for people to need different saddles or different handlebars. It's also pretty hard to predict the right bike size just from someone's height.