You have a tough order to fill. Western styling and semi-auto are rather difficult to find in the same package. There are a few rifles that might fit the bill, you might run these by her and see what she thinks.
Marlin Model 60 - (Marlin
) At the low end of the price spectrum and by all accounts seems to function reliably. I have never owned one so I cannot attest to the accuracy, however they have been in service for a while.
Ruger 10/22 Classic Carbine - (Ruger
) This is a special run of the Ruger 10/22 that is being done by Talo. It is supposed to be modeled after European styling, but it has a western feel with the straight grip. The nice thing about the Ruger is there are parts damn near everywhere. There are also a lot of people around who work on them since they are so simple and modular.
Browning Semi-Auto Grade I - (Browning
) This would be the high end of the spectrum. This rifle has been around for a very long time, so it might be possible to get a nice condition used one, though YMMV. This rifle is a real classic and it would be hard to go wrong.
Just my $.02, but I would be proud to own any of them. Hope this helps.