Explain what Violet means by the days at the hospital being salad days.

Violet says the days at the hospital are like salad days. Salad days is a common term used to refer to a youthful time when things are ideological and simple. Violet, being clearly more intelligent then her new friends, knows this phrase, and knows that these days come at the cost of their innocence. She understands that the days of youthful naivety all too soon disappear.