You should take this opportunity to get a medical note from your psychiatrist explaining that you are unable to care for your mother-in-law as it would deteriorate your mental health.
Then present this letter to her current care facility facilitators and ask them to make permanent accommodations for your mother-in-law.
I don’t blame you and in fact think you made a good decision. When in an airplane and the oxygen masks come down you put yours on first then the child beside you. You need to help yourself first before you are in a position to help others.