I recently got a Sugoi rain jacket made for running that would work for both walking and biking. The underarms are made of breathable fabric, so you don't get too hot, but the front, back, and shoulders are rain resistant. Running stores seem to be putting their rain stuff on about now.
As for shoes, they do make rainproof hiking shoes, which after 25 miles might seem like heaven. I know Merrill makes some. Or alternately, you could go with TEVA sandals or the equivalent, so at least if you hit a dry spell your feet will dry. Wet shoes while walking really does make you miserable. The rest of you can be wet, but dry feet will make the difference.
Too late for Saturday though. One thing I know for sure is not to wear new shoes before a 25 mile walk. Anything that doesn't fit quite right will make you very unhappy.
I believe it is a 10 mile walk and then a 25 mile ride. But you are right about wearing untried shoes. It would be better to put some kind of bootie over them.
Whatever she uses, for both feet and body, it had best be breathable, or she will do a lot of unwanted sweating.
