It is the grey line of being sick. You don't say the temperature, is it 99.8? If so, I would keep her home. Remember, a temperature is usually a reaction to infection somewhere in the body.
In our house, we push ourselves to keep going, but it is hard with kids, because they don't know their bodies like we know ours. Not yet.
My daughter is home today with a the tummy bug. Her stomach hurt but she never got sick, so she went to school yesterday. I picked her up and she said her stomach hurt and just before bed she threw up. I had already called in sick last night and she woke me up at 6:00 a.m. and said she was ready to go to school. I tried to feed her and she couldn't or wouldn't eat a plain warm tortilla. So I kept her home.
Yes there is a risk that others get sick, but hopefully our immunities work hard to keep the healthy healthy. I am sure I come in contact with sick people all the time. My niece works at a pharmacy and she never gets sick.
As well, we only have so many sick days at school and work. Personally, I think you just have to establish some guidelines, while staying within the schools policy.