Re: Fifths disease
Around here, they don't even exclude in schools for fifths disease. Most kids have had it well before this age, so I wouldn't exclude her from any activities unless she feels crummy otherwise.
The rash on the arms and legs can last longer than the face rash, but it probably not contagious.
Most of us had this rash years ago, and because it's so mild, we never even knew we had it.