The woman Brooke Mueller allegedly assaulted at an Aspen nightclub back in December tells TMZ, Brooke doesn't belong in rehab ... she belongs BEHIND BARS.
TMZ broke the story ... Brooke's not looking at any jail time whatsoever after her Aspen arrest -- because the issue of confinement has not been part of plea bargain negotiations between her lawyer and the prosecutor.
But Llana Little -- the woman Mueller allegedly assaulted the night of her arrest -- is furious about the situation ... insisting, Brooke "should go to jail" for hitting her.
Little tells us, she was coming off the dance floor inside a nightclub on December 2nd -- and accidentally bumped into Brooke. Words were exchanged, and when she turned around, Little says Brooke punched her in the back.
Brooke then left that club and went to another one -- where police eventually dragged her back outside and arrested her for cocaine possession and 3rd degree assault.
The woman -- a key witness in the Aspen case -- adds, "She needs to learn her lesson that what she did was not okay."