If it was me, I'd soak a towel in acetone and lay it over the thing to strip it, then start over. You can't shoot raw thinner at it in an attempt to melt it back because you'll ruin it. It'll bubble and boil and turn to shite. While it's fresh, it's easily removed and it won't hurt the foundation, so your wife's work will be preserved.
Don't shoot it again unless the humidity is lower than about 65%. The milky result came from the expansion of the spray vehicle, which lowers the dewpoint of the air and causes condensation.