a good camping knife. the best hiking shoes you can afford. a reliable way to start fires. a magnesium starter is a good choice. a good reliable light source. rechargeable flashlight or the like.

Is this the first time for your friend, too?

Lightweight backpacking tents are very expensive and still add to your load considerably. Since you're out in AZ I don't think you'll need it. Make sure your sleeping bags are good enough for the low temps you'll be seeing.

And if you use a magnesium starter, make sure you've practiced with it before you leave.

I'll second what everybody else has said and add:

Take a map of the area, preferably topographical with marked trails. And a compass or GPS. Learn how to use the compass or GPS and map.

Comfortable shoes, thin "liner" type of socks (not nylon), thick padded socks. This combo will help prevent blisters. The liner socks wick away moisture (polypropylene is best) and move with your skin to reduce friction. The padded socks provide cushion and comfort. The comfortable shoes should be worn in, not brand new. If you buy new shoes wear them for a week everywhere you go.

Make sure your first-aid kit has moleskin. Use it on "hotspots" if you do start to form blisters.

LOL...yes, indeed.

a little magnesium goes a long way

If they're backpacking in AZ, I'm not sure open fires will be an option.

tracilicious, you should check on the restrictions of the area where you'll be backpacking and also be aware of any ranger warnings regarding wildlife or weather conditions.

Also, if you take disposable wipes, those should be packed out as well.

Fires aren't usually restricted until Summer here.

My friend is an experienced backpacker. But we haven't had a great deal of time to plan this and her phone is on the fritz.

These are good suggestions, thanks guys.

I don't think freeze dried foods are for me. I'm vegetarian and really prefer fresh food. Wet wipes, definitely.

Fresh food takes up a lot of space and weight. Dried fruit is a good compromise...

How much ground are you planning to cover in the hiking?

Is it something like hike in 7 miles, camp in the same spot for two nights then hike back out or more like a 10 mile per day grand loop tour of some area?

That would effect how much you might want to compromise on the fresh food thing. But one thing I would recommend even if you want to avoid heavily processed food is a trip somewhere with a good dry bulk selection (like Whole Foods). Consider dishes that you can premix all of the dry ingredients then just cook in water. I've done a lot of good pasta and stew dishes where I put all of the dried ingredients and seasoning in Ziploc bags at home then just add water for cooking.