Bike for wife recommendations. Lightweight hard tail
 

We are in our 60's and my wife's having issues with her hands, (not fit issues). One of our favorite rides involves two 7 mile climbs on a dirt road with accompanying descents. The descents on the rough road are hard on her hands, particularly the braking involved. She has two different hard tails, neither of which have suspension forks and both are steel. She's 5' 4" and rides a small frame, either 15.5 or 17.5 depending on the make and fit. I'd love to find a carbon frame with eyelets for racks but that doesn't exist. A carbon frame with a seat post rack may be enough room for her stuff so that's an option. A good quality aluminum frame with a light rack would probably be more to her liking as she can carry all her own clothing and gear. The ride is in remote wilderness so extra clothing for safety and such is needed even though it's only 35mi out and back. I figure a suspension fork that reacted to relatively small rocks, and a lighter bike, along with tubeless tires inflated lower than she normally uses would go a long way to softening the ride over her current steel frame with no suspension. I've assumed a rear suspension would do little to alleviate hand issues.
I'm looking to spend between 2-4000. No more. Locally we have Trek and Specialized dealers and maybe Giant nearby. Kona too but no smaller brands I can think of. Any thoughts or recommendations?

What does she have now? Could always add a suspension fork to that assuming the geometry won't be thrown off too much. A nice light 80mm travel fork should be plenty. Throw some good hydraulic disk brakes on it if it doesn't already have them.

Any preference in the wheel size?

For a 29er...maybe look into a Niner Air 9 carbon. At 5'4"...she would probably on a small.

Carbon isn't typically rated for weight bearing, when you get to carbon bikes, they are designed for racing and sportive riding.
Full suspension definitely isn't going to have rack options, due to the way the rear triangle moves about.

Good Shimano hydraulic disc brakes require very little strength to get good stopping power.

Trek typically has very good aluminum bikes that still retain rack mounts. lets see...
Skye SLX - Trek Bicycle
"WSD Alpha Gold Aluminum w/semi-integrated head tube, mechanically formed & butted tubing, rack mounts, internal front derailleur routing, G2 Geometry on 29ers"