Hi Deb, Welcome back to the fun world of painting! By doing so, you'll be happier, art is a theraphy, is a healing process. For your beloved sister, a water filter for the kitchen and the shower will be best, taking in consideration her condition. LED is the killer, another big carcinogen, not many people realize that we need a water filter for the shower, no matter how the city states that the water is clean, is NOT.
An air filter for the entire house, besides air condition, is highly recommended. Distilled water is the ideal when doing watercolors and acrylics. the Colors will pop up like making pop corn, Best regards