My daughter has been on antibiotics since last Monday for respiratory infection. We had plans to go yo some friends house to watch kc game tonight but just found out their daughter has fever. Her mom said my daughter should be fine since she is already on antibiotics... wondering if that is true?

NO, it isn't. Antibiotics treat ONLY bacterial infections. Colds and the flu are viral infections, which have no cure.
On the other hand, your daughter may only have a viral infection, and was given antibiotics simply because too many doctors hand them out easily when they shouldn't. The virus runs it's course and people think the antibiotics worked.
I'm not saying she doesn't have a bacterial infection, just that she isn't immune to anything.
So - get a babysitter or stay home.

No, the mother has no idea what she is talking about. A mother should never have child with a fever should not be around other children.

The reason schools normally send children with fevers home

No, you daughter isn't safe from this other child. Antibiotics don't prevent you from getting sick, they're supposed to cure what you already have. Just because she's on antibiotics doesn't mean she can't catch something else.