Help with finances. Any advice?

I retired from my legal secretary career of more than 40 years at the age of 64 to care for my mom (I just turned 67 a few days ago and she is going to be 101 shortly). I decided to do gig work for the last few years because I could work my own hours and be home when mom really needed me. Now, she REALLY needs me at home so I cut my gig work back to two days a week (my sister watches mom those 2 days, bless her!). Problem is that cutting out 4 days a week has seriously imperiled my finances. I pay all expenses, mortgage, utilities, groceries, etc. Mom uses her monthly social security check for her personal needs, which is how I like it. I don't like the idea of her paying for anything. However, I have asked her if she would be willing to help out to the tune of about $150 a month and she said she couldn't afford it. Mom has substantial savings which we will use for funeral expenses when the time comes, and she will also be leaving a small inheritance to my sister and me. Her personal expenses come to about $350 a month and her SS check is $1400 a month. However, because I have now too much month at the end of the money, would it be unethical of me to use the $150 I need to get us through? Mom has mild dementia and does not fully understand the current situation. I value your opinions, I don't want to do anything wrong or unethical.