At this point... don't know what to tell you. I have worked for b6 before. They think... especially those born and raise in BJ, think that they are big and "can cover the sky" and "walk like a crab".
Do what is in your best interest. You cannot predict consequences either way. If Y decides she will take all the responsibilities, let it be. What it boils down to is that you have really lost things and someone in the house has really gone through your things and have taken them.