You may have already a 27.5" wheelset, but why not a 29" ?
It rolls better in theory.
The Tideace M009 is a really nice a cheap frame. The paint job is excellent.
A friend has it with a matching rigid fork, it makes a very light ~7.5kg bike, and she is very happy with it for soft mountain biking/gravel/city.
However a proper fork would be needed if your wife like to bomb rock gardens