Look at how often it rains during her intended commutes.
In the Netherlands, which is known for 'always being rainy' you need your waterproofs about 6 days a year when commuting 5 days per week.
A little drizzle should not stop a person from riding when a good coat is used and a hood/hat or helmet with rain cover if a helmet is the norm where you are.
A good set of waterproofs which is easy to put on and take off is more useful than a cover that always catches wind and will likely not protect against rain in side winds.
Plan the route (as far as possible) such that the quiet roads or bicycle paths are used and busy roads are crossed at traffic lights or other 'easy to use' points.
Try out several bikes, rentals or loans for a few days if available.
Have her try out bike seats in different heights.
While she is still unsure about riding, easy access to the ground is good. But the ride will be easier/smoother when the seat is a bit higher up. So I would suggest a bike that allows both, the lower position and the 'proper' high up one.
If she is really not able to ride a two wheeled bike, think about a recumbent trike. Those are available with e-bike tech as well.
Not only is the bike stable, also the position of the rider on the bike is stable.
I have used a recumbent trike for 5 years, just for the fun of it, and can certainly recommend it. You are lower down (gives more stability) but you are wider and when viewed really seen.
I would not go for the extremely low ones, but for one about the same height as a dining chair.
Yes, you get wet when it rains, but are you made of sugar?
I survived getting rained on all my life and still commute by bike.