I would 1st use HOT water with a bit of baking soda all over the walls, then the Simple Green that SB suggested, also as Riley said, leave the closet OPEN after & before each dousing/cleaning...the last thing would be to use clear water to get any/all residue off prior to repainting. If there is carpet in the closet, pull it up (best case scenario) if that isn't an option, steam clean it rather than shampooing, shampoo leaves it's own residue & steam cleaning actually removes the mess/dirt/smell. If you have a hardwood floor in there treat it the same as the walls (it's a closet so no worries over the shine, course you can redo the wood after cleaning, shine wise that is with a product for that). Make sure you get the bar & shelves in there as well. Keep her clothing out of the room until you are finished. If it smells now too, unfortunately you will have to rewash it now...UGH...how I HATE the smell of smoke on clothing! :/
The 'new' paint should be 'old' paint by October, so PAINT AWAY after cleaning!
Whatever you decide to use/do make sure you do it in small spurts & with the room open preferably an open window so you don't sicken yourself or overdo, mama! ;)
Congrats!