A concern I have with recommending that bike, and why I would not, is that it is probably illegal wherever the OP is. It OP did not give a location; So, I am going to rely on the laws where I am as a guide (remember, the answer to the "whose laws, which laws?" that people like to interject into this forum is "in the jurisdiction where it is applied."). Remember that you would need to check the laws where you are, and the guys at the bike shop are usually not very knowledgeable.

All that being said, the law in the US, and in the states I operate, in say 750W. To get to most out of the power you have available, no matter how much that is, you should go through the gears. I am on a bit of a mid-drive kick and recommend them. The BaFang BBSxx series is very well regarded for its simplicity of installation, performance, and reliability.

If you are convinced on a hub motor, and there are arguments for them, you still should stick with the rear wheel unless you have a very specific reason for not doing so. There several rear wheel conversion kits, there is even one that features an internal gearing hub.

Yes, I am pointing at kits. I recommend getting a bike she likes, and then adding a motor to it. First, it may be cheaper (depending on DIY and shop rates). More importantly, you are more likely to get a better base bike. There are very good, ready to ride, e-bikes on the market however, they tend to be expensive. The lower priced e-bikes are generally built on a poor quality bicycle.

Use the bike linked to in the quote on this post as an example, It has brakes that I would not consider for an e-bike. With the increased speed the e-bike is frequently going to be used at, disc brakes, or name brand drum brakes, are a necessity. Some will say that rim brakes are fine; yes, immediately after leaving the shop they may work reasonable well. However, for most riders they do not offer consistent, reliable, stopping power.

Second the fork is of noticeably poor quality, remember, on an e-bike you are going to be pounding the parts harder. I could keep going; but the point is there, many manufacturers of low price e-bikes use very poor quality bikes as the basis of the product. They then try to mask the poor quality of the basic bike by using an illegally oversized motor.

Yes, there are exceptions to the comments I made above; but if you are just starting out, you are unlikely to find those exceptions (and I cannot think of any that are step through models, that is why I am not point you at any of the exceptional products). Start with a good bike, then have it converted, you will have a better quality, and lower priced bike when you are done.