I wouldn't personally head to the Blue Range in July. It's a little bit warmer than I prefer, and it is very likely you will experience thunderstorms everyday. Not to mention it's a very long drive!
You're asking for a few things that contradict each other unfortunately: It's 4th of July. Places that won't be unbearably hot will likely be at least somewhat crowded. That's just how it is here in the summer. Especially on a holiday weekend!
I really think one of the better options is the popular
Cabin Loop. It won't be crowded, but you'll almost certainly pass a few other groups of backpackers. The catch will be whether any of the ideal camping areas near the springs have other groups camped nearby or not.
There aren't expansive views up there but it's scenic pine forest with picturesque small canyons and ridges.
Not knowing your experience level, it's difficult to recommend much else. Some people like to spend a night or two exploring up the
West Fork of Oak Creek Canyon. You have to go quite a ways before camping is permitted and you will have to be walking in water much of that hike.
If you don't mind a big climb, great views can be found in some of the sky islands of southern Arizona. I might recommend the Huachucas. A
Carr-Comfort Springs loop features some big elevation gain to start, but there are some great camp spots along the ridge with great views, and I'm pretty sure
Bathtub Spring is reliable year round. A trip over to Miller Peak would be a nice side trip/day hike on this loop.
But, if she says yes

it won't matter where you are. It'll be perfect just because it is.

Good luck!