I also have a daughter with body odor. She was around 3.5 when I started noticing it, maining when she was hot. I giveher a bath everyday but still noticed it. I talked to her doctor about it and he stated there was nothing to worry about because she had not other signs of earlt puberty. At about 4 years old, I began to have her use just deoderant. It is had to find, but all the research I found was that the antiperperant was what caused problesm so I thought if I got one without the bad stuff I'd be ok. I found an all natural one at Target that was just doederant and it has worked wonders. She is now 5 and it has just become part of her morning routine to put it on. If she goes to family to spend the night, she makes sure it is packed. I tried the scented powders and they did not seem to work either.
Hope all works out. To ease your stress mention it to the doctor and see what they say.