Can girls use だよね in everyday conversations?
Certainly yes, girls can use だよね, but it may leave a slightly tomboyish impression. The first Japanese hip-hop song which sold one million records was called DA.YO.NE and is mainly performed by a girl.
On the other hand, boys can use だよね, too, but IMO it's mainly used by boys who always stick to 僕 instead of 俺 as a first-person pronoun. (I mean, it sounds a bit gentle or "pretty.")