Remember she was already a well gifted padawan for her age when she was turned over to Anakin. I know in AOTC, Anakin was assigned to "bodyguard" Padme which was "his first assignment" alone. So Padawan's do get their own assignments. I feel Yoda paired them up more for Anakin's sake, then for Ahsoka's. I think they were trying to "ground him" better. But unfortunately it completely backfired and only sent him down the dark side path further.