I would imagine she really didn't get the full effect of what your walking out meant so don't be too hard on yourself.

I totally support anyone who removes themself from a situation where they are being treated disrespectfully but with dementia or psychosis I find it really important to have a thick skin and not take things personally.

She clearly isn't in her right mind and the truth is you were a great daughter in law to do all that shopping for her so I would hold on to that and give yourself the credit rather than expecting her to be appreciative.