[Sorry, you can just skip this first paragraph if you'd like. It turned into a bit of a rant.]
Rad does publish the reach of the RadMini ST2 as 16" but it isn't a very good reference number. Rad seem to be saying, "if your arms are at least 16" long, you should fit," but that isn't traditionally what reach means. For a real-world comparison,
this woman states she is 4'8" and looks fairly comfortable and upright riding the prior-gen Blix Vika+, though the seat is at it's lowest position and her legs are near full-extension. However,
the published reach for the Vika+ is a much longer 23.8". You can see from the illustrations that Rad and Blix are measuring from different points on the bike, resulting in such different numbers. Looking at the rest of the numbers, these are two similarly-sized bikes.
All that aside, your best bet might be one of the
Bike Friday bikes, which are unique because they have adjustable top tubes that allow you to adjust the reach to be very short. It's going to be more expensive, but that's because Bike Friday is a folding bike company that offers electric conversions. I've ridden a Bike Friday, and they are good quality, fun bikes. Also, unlike Rad or Blix, you can call them up and custom-order a bike that best fits your sizing and needs.
Other than that, you may try asking around on the
Tern,
Gocycle, and
Qualisports forums, as those are all folding ebike companies.