Note: I am a recumbent owner. Mostly...
All upright bikes are pretty much alike, except that the really expensive ones are lightweight--which does nothing to improve the riding comfort.
The most comfortable "mostly" upright bikes I've heard of so far is the RANS crank-forward bikes. Prices start at around $1700. I've had a RANS Fusion for 10+ years now; it is the only upright bike I own.
There's other cheaper bikes that are kinda-sorta like that. But they work like crap.
A bicycle that hurts to ride is no bargain at any price, and the #1 reason that people don't ride the normal bikes they own is because of the riding discomfort involved.
You can go cheap if you want--lots of people do--but the money you saved won't make your butt hurt any less (nor will it keep her riding).