That word does not need to be used in the public presence of schoolchildren, no matter what sort of philosophy or religion the school. It's simply unprofessional and inappropriate. As a preschool teacher, there's actually a little "no swearing" switch that seems to flick on in my brain around kids. This doesn't mean that an occasional "sh*t" doesn't slip out at home during family time, but I do correct myself, apologize to my son, and try to model better ways of expression around him.
Having to hear swearing during a soccer game? Sounds like she has some anger/emotional management issues. Kids of any age shouldn't be sworn at for losing a game. I'm sure that improves morale. The fact that she isn't curbing her language at school and feels comfortable dropping the F-bomb in a professional capacity is worrisome and should be addressed. For everyone's sake. Maybe it's time for the parents to start talking with each other and finding resources to address this, or maybe it's time to move to a new school if the principal isn't censured or removed. (Does the principal 'run' the school or have some sort of ownership/investment in it? Just wondering...)
And if you feel there are problems with 'how' she is handling the children, that is a bigger issue. You might give your local school board an anonymous call to see what sort of regulations/options/standard guidelines there are for this. Sometimes, schools do better when these issues are addressed to the board. I hope your daughter's school has more oversight than just this principal.