For your own benefit, I would go for a human hair wig after all, and convince her it's the best option. Synthetic hair does feel different, get tangled easily and has shorter life.

IMHO, Russian hair is the softest and has the best "touch" (I wear wigs), but Brazilian or any other would work too.

Depends on where you live, I would actually consider going with her to a wig salon, and check what is available, or even order a custom wig, if money is not an issue.

Make the wig buying a fun thing for her too, do some wig try-on event.

And enjoy!