As someone else already posted, if you wheel it, you're going to break it. You're also going to scratch the paint, dent the sheet metal, and generally reduce the value of the vehicle exponentially. That may be fine if you end up marrying the girl, but if you break up she'll be stuck with a beat-up Jeep because you wanted to go wheeling.
I totally see where you guys are coming from and would have tried to make the same argument if I had gotten to her sooner. However she if she is going to destroy a brand new jeep anyway, with or without me, I might as well go along for the ride. The spotless 2000 cherokee she bought last year for $12000 with 30000 miles never having seen a speck of dirt is already almost a complete loss. I've been told maybe 2-3 grand. This isn't trail damage either she just crashes it once a month. The engine knocks, the T-case makes funny rubbing noises and there isnt a straight panel on the whole vehicle. We dont even wheel that much, maybe once a month a light trails. I do drive it when we go but I don't just take her jeep wheeling and leave her at home. In the case that I did break something I do have the ability to pay for it and most definately would. I just dont have the money to support another vehicle of my own that I know i couldn't help but pour all of my money into. I dont really plan to put that much into hers but when holidays and special occasions come around forget chocolates she wants stuff for her jeep and we do both enjoy it.