1) Does she want to be able to get exercise still?

2) What kind of hills are you dealing with?

3) Do you feel like building her something and feel confident you can do it safely?

If she wants to exercise, torque-sensing pedal assist is a must. Cadence sensors mostly only let you spin your legs as the motor powers you along. A torque sensor can make you feel like Superman on a bike but can get you a great workout at the same time. I personally really wouldn't build ir buy an ebike that didn't include a torque sensor, it really improves the experience that much.

Extreme elevation changes call for a mid-drive ebike, otherwise hub motors are most popular and preferred by many for a few different reasons. Mid-drives are hard on the bike components for instance. A hub motor can still tackle a hill if it has decent wattage, the limit in the US is 750w which is plenty for all but the most extreme of hill climbing.

If you decide to go DIY head over to /r/ebikes. If you want to buy a factory ebike, I spent a few months researching and shopping online and ended up going with Juiced Bikes. Direct to consumer can get you a lot more bike for the money if you can deal with the nature of direct to consumer bicycles by mail. I can say their customer support is great, they are good at resolving issues/honoring the warranty, and the bike comes 95% assembled which helps. I bought a CrossCurrent S, it's one of my favorite things in the world. Ridiculously fun. It's also my only form of transportation and is making for a great commuter these past several months!