The diesel is nice, my father in law got one a couple months ago. He says he gets 31-32 hwy. Kinda wish we'd have looked at one before getting our '14 GC.
As for household income, I make what I consider to be pretty good money, especially if I count side work, but, my girl makes about 50% more than I do. I ain't mad at her! She's definitely a boss, just not my boss [emoji41]
All depends on the people in the relationship, everyone contributes in different ways. For instance, "her income" has paid for much of our remodel materials, I've done every bit of the work myself, which would have cost at least that much. Together we've gained a good 60% in equity on our previously bank owned home.
Buy her what she wants OP (within reason lol).