Trouble dealing with feelings of anger

Hi I'm new here and just need to vent a bit. I am currently dealing with my mother in law (mil) who has been diagnosed with Alzheimers. I have been married for 22 yrs and quite frankly she was never very nice to me before her illness. She lives with us. I am having a lot of trouble dealing with my feelings of anger. I work 9+ hours most days I try to do meal prep for my work food she takes the food I make and puts it in her room leaving me nothing for work. My husband and I gave up our bedroom so she can have the largest bedroom with the bathroom. She consistently throws away things that I need. Tonight she threw away my rolling pin. In December she threw away a $3000 check that I requested for a 401k loan before that she threw away a syringe that was the only measurement for my sick cats meds. He is an only child and I am at my witts end. She is not bad enough for her dr to warrant institutionalization because she puts on a good front in public. How does everyone deal with this?