My 9 year old daughter has body odor, any deodorant suggestions for children? Should we be concerned?

Andrenarchy? The first signs of puberty beginning is axillary odor. The adrenal gland begins producing androgens that mature sweat glands and sweat production begins. Good hygiene is necessary as well as deodorant use. There is nothing to worry about unless the child has other significant secondary sexual characteristics such as thick pubic hair, breast growth, vaginal discharge, acne.
Deodorant. I would recommend standard women's deodorant and being sure she is actually bathing correctly (soaping body and shampooing hair). Children of this age group often need to be taught hygiene with supervision to ensure proper adherence.