There are several white/whitish roses that do 'well' up to a certain temperature in the low desert. One of the best is Iceberg; fragrant, not prone to pest or disease. Moondance has received favorable reviews from local rosarians throughout the Valley. The own-root shrub, Pillow Fight, is a descendent of the mini Popcorn, and is considered a near-constant bloomer. One year, I cut off over 85 blooms from one bush at pruning time. Best white floribunda, IMO, is Fabulous. Can take a lot of heat, blooms have great substance and fragrance, bush seems impervious to pest or disease, including thrips which favor light-colored roses. J&P released it a few years ago then pulled it from market then reintroduced it again. With the rumor that J&P will be filing Chapter 7, may be tough to get from any source. White hybrid teas; Pope John Paul II, Honor, JFK, Whisper, etc receive less accolades from those of us with no-spray gardens. During the spring bloom cycle, thrips can destroy every bloom. Of the David Austins, I have Fair Bianca. Heat isn't a friend to the fair lady but maybe if she was shaded from the afternoon sun. Some of the David Austins with Mary Rose in their parentage may present a cane or more of Mary Rose within their second year. Interesting habit. The noisette, Madame Alfred Carriere, shrubs Sally Holmes (often more pink than white) and Sombrueil (aka Colonial White) also do wonderfully in this area. All are considered climbers and MAC and Sally Holmes can claim a substantial portion of the garden. These do best without regular pruning. Locally, Bakers, Berridges, A&P, Harpers and Summer Winds tend to carry quality grade #1 roses. Big box stores may receive grade #1 roses but that's the extent of their interaction with the rose... receipt of it. The nurseries trim the roots, water them (bare roots have gone without water for about 2 mths) and pot them or at least cover their roots in west sawdust.

You might tell her to try something like Altissimo, a beautiful, single (5 petals) red rose, or maybe Climbing Pinkie, which is a little larger and should also be okay in your climate. Pinkie has clusters of small pink fully-petaled flowers and is probably the more disease-resistant of the two. But, be aware, no rose is going to be disease-resistant or flower well with less than 5 or 6 hours of direct sunlight a day.

I did a quick search of the archives at the Master Gardener site for Maricopa County and didn't find what I was looking for... Maybe if I call them? Thanks

Ortho puts out an excellent soft cover book called, "All About Roses". This reasonable book has straight forward information on all aspects of growing roses.