Dagny's sister is in Portland OR, I have a feeling that finding water to purify won't be an issue. Rather than carrying a Silcock wrench, a small water filter may be more useful for long term water treatment. I have an MSR MiniWorks; it "screws onto an MSR Dromedary® Bag or Nalgene® water bottle". There's lots of water in Portland, it's just a matter of making it drinkable.

That said, since your (petite) sister will not be carrying a bag with lots of gear, size this kit to assist in getting to the larger kit in her car or as a GHB. Think of it as a walking kit with a destination -- car/home. The bigger kits reside where you use them.

What is the elevation of her home? At what elevation in Portland would one be "safe" from a serious tsunami?