... at her age, does she know... about stranger danger and what is private and about inappropriate touching? It seems she does not, at all.
It is not only about how 'she' needs to protect herself, but rather IF she knows what to do, if something happens.
Its good you told her to "tell the Teacher first, then the parents." BUT... it is NOT a 'child' who should be telling the boy's Parents. A 5 year old, needs the parent to ALSO, take care of it.
And YOU need to tell the Teacher, not only your daughter.
Don't leave it up to a 5 year old to do all this, they are still very young and cannot handle adult decisions nor even know how to handle it.
In any case, she told you a boy in Kindergarten touched her privates... so, you need to now, TELL her Teacher. And/or put it in writing.
There is no telling, what happened, but the Teacher should know that a child was touched. It is not up to us to decide, whether it was just kid type typical behavior or not or if it was something really weird/inappropriate.
You daughter did not tell you exactly what happened... nor if this boy did it once or often.
all the best,
Susan