I'm in the area, so a hassle free test ride looks fair. Do you have any data to prove the 10 miles range claim? That would help me decide, especially if you've ridden one? As a lot of ebikes are circa 24 Kilos, 50% heavier than the Gtech, what about power to weight ratio, is that not a factor? I did say earlier I live on the Somerset levels and hills are just not around, except for bridges over the M5!
SW uses a lot of power but he mountain bikes. Often over 20 mph.
Your wife we assume will be sedate at 10 mph. That means the bike will always be assisting. So steady battery drain. Not as dramatic as SW,s but range limiting.
The power to weight ratio is for the bike and rider together so if your wife weights 50kg and bike 15 or 25kg the total weight is 65 or 75 kg!
Not such a huge difference.
On the flat weight is of little concern. Battery power is important the bigger the battery the better.
Something like the carrera has a larger battery, so it can keep helping for longer.
YOU could put it into a gear and the wife would pedal it like the GTech
If she then says can't it go faster or up hills easier you could change the gear again. Or perhaps she might do it herself and discover how to go further easier in comfort.