37.8 is only slightly raised, it's not like it was 40 or something! My son's temperature has generally been about 35.8 when i've taken it when i've been worried. When he was ill before xmas it was nearly 39 so then I knew I should take him to the doctor, although I could tell anyway. You know your own child and know if they're ill without taking their temperature, and the thermometers aren't always that accurate. We have a digital one from Boots that you can out under their arm. I'd take her to the doctor if you think something's wrong, but if she has a cold then there's not much they can do. Xmas was the first time i'd taken my son to the doctor and he was 18 months old. He was throwing up and was really not himself - that's why I took him.