My 2yrs old pom/chi mix seems to enjoy tormenting my autistic son. Any ideas?

Cookie has become somewhat aggresive towards my 28yr old autistic son. She will wait outside his bedroom door for him up to come out then will pounce on him, barking, nipping at his feet & legs. Then she will run downstairs to her bowl & gobble up any food or treats like she is trying to keep them from him & if he attempts to pick up one of her toys she will attempt to bite him. It's obvious she can sense the differences in him but he is by no means aggressive towards her & even feeds & cleans up after her. She does this constantly and I havent a clue how to stop it...