Thanks for all the suggestions. She is very familiar with Maui and the Volcano so I think she's aware of the cold descent issue but I'll be sure to remind her. Maillotpois, the altitude training tips are great. Thank you.
I'm going to see what kind of climbs I can find that get her up to 7000'. I may sense a road trip in the future. 
This client doesn't work and finances are not really an issue. She is not into camping at all. Anyone have suggestions for a destination, riding trip that would include some elevation and a nice place to stay? The Sierras are a possibility but I wonder if there is something closer.
Living life like there's no tomorrow.
http://gorgebikefitter.com/
2007 Look Dura Ace
2010 Custom Tonic cross with discs, SRAM
2012 Moots YBB 2 x 10 Shimano XTR
2014 Soma B-Side SS