My 3 year old daughter has a fever of 103 what should I do for her

Put her in bed with lots of blankets and propped up on pillows so she can breathe, and give her lots of weak juice or whatever she wants, as long as she keeps hydrated.
Fever of 103 in a toddler isn't as alarming as in an adult, but call the doctor! Even if to find out if it's OK to give her children's aspirin or not.

You should give her a fever reducer (such as infants tylenol) and give her a cool bath or compress to help reduce her body temp. If this doesn't take her temp down then go to the ER.

I did some reading, and the old days of either extra warm or cool bath are both no longer recommended - normal amount of blankets.

A fever of 103 should be seen to by a doctor immediately. At 105 you're looking at possible brain damage and death. This is not something you should be trying to deal with at home. She needs medical attention.