Some responses I've received. The first quote is from our (unofficial) local, cloth diaper expert. :)
"if its city water then planet is an excellent choice, thats what i used in Brevard. When we moved over here, I had to switch to tide after a few months because of the well water. If she's only staying a short time, id think she would be fine with the planet. It was long term build-up i was having trouble with."
"According to my DH (who works for the City of Asheville's public works) Black Mountain does have their own municipal water system, so if the reunion is in the city limits, she'll probably be using city water, not well."
"I don't know what black mtn water is like compared to AVL but she's probably fine. Just use a tiny, tiny bit. I'm kind of of the opinion that a wash or two on vacay isn't going to do any permanent damage."
"I use well water. It's not as "hard" though as some water from wells I've experienced. We use plant based detergent too and clothes are always clean. "