Well, if you want a thread discussing some of this, here's one:
https://forum.mrmoneymustache.com/share-your-badassity/making-the-commute-switch-e-bike-on-the-way!/I'm not an expert, but if she's talking about a 1 mile commute, a Level 3 bike with a big battery is probably a waste of money. I'd think that a conversion kit would be a much more frugal option, but I haven't done it before. Some on this forum have.
Long-term reliability of a purpose-built e-bike might be better than a conversion kit (frame theoretically is designed to handle the extra weight/speed), but with such a short commute just about anything should work. Many thousands of miles should be expected, with reliability similar to that of a regular bike. Worst-case scenario, something goes wrong with the electric components, and she has to pedal a heavy bike for half a mile. In general, it's a lot more likely that something goes wrong with the 'bike' part of the e-bike than the 'e-' portion. Regular bike maintenance needed as for any bike.
You might check out electricbikereview.com if you want to read up on a lot of e-bikes. Dedicated forums there as well.