although I have been called a dirty dolphin from time to time, that doesn't work to tag me!
I'm sure there are tons of plants that could work.
Does she want flowers? foliage? both? Will she irrigate some if it doesn't rain?
How big is the area? how big are the biggest boulders? How much space does she have for planting between them? and how deep is the potential root-run for the plants?
I mean yuccas get huge and make huge roots compared to semps
Personally, I like a variety of stuff--
consider the bulbs: early spring types--many little species tulips could naturalize and don't need a proper winter to perform well, allium loves a well drained soil-- some will fire in the early spring, most later spring, and a few in the summer and even later, fall bulbs--saffron crocus? maybe even some lilies?
Other creepers like creeping thyme and veronica? delosperma, dianthus?
Tanacetum densum ssp. amani, aka Partridge Feather loves shallow rocky soil--I know it grows in the PNW and handles the rain okay but I don't know how it would do there. It is indestructible here and very good at stabilizing slopes.
Irises
little dwarf conifers?
rock daphnes
salvia and agastache--many different kinds and some great smaller varieties
and a whole lot more exotic stuff
Hopefully someone more knowledgeable can offer some more ideas
She might be able to do more of the tender-type succulents if she's into those
