I'd say a 30x9.5" tire is going to be her best bet. 31s would fit but that 4-cyl will have trouble spinning up on the street and it will kill her mileage. Stock rims should be 15x7 and will fit these tires just fine. High-Tec Retreading
has some nice tires in the sizes you are looking for. $40/each for 30s and $45/each for 31s. Everything from AP, AT, MT, and OTR tread designs (I really like the looks of the OTRs). I got a set of 30x9.5 APs for my daily-driver '89 Comanche and promptly drove them to Tellico and back, a 640+ mile trip each way. They rode fine and performed decently on the trails. They cost me $230 shipped to my door.
Now... if she ends up wanting a set of aluminum rims, go to the junkyard and grab a set of Ford Ranger or Bronco II rims. They should run you about $20/each. Get aggressive 31x10.5" tires for them and she'll have a seperate set of street tires and trail tires.
Here's a picture of my Comanche with the rims I'm talking about. It's got worn-out LT235/75R15s in this picture. The 30s look much nicer. The 237/75s do have much less mass, and most of this is in the side-wall area and I wouldn't skimp there...