Just because you stop trying to fix everything or walk out of the room doesn't make it a boundary. The validating, letting her problems be her problems and not taking the bait is all good and neccessary.
A boundary is when someones behavior is unacceptable to you then you state what the consequences will be if they continue that behavior. Google "Crucial Conversations" and "Crucial Conversations." Look up boundsaries in relationships as well. Do your homework.
M22,H45,W45 S21/18D12 Retain faith that you will prevail in the end, regardless of the difficulties and at the same time confront the most brutal facts of your current reality, whatever they might be.