At hospitals they have blue pads that they put under them or you can buy rubber sheeting with fleece on one side and cut to cover the sheet where she wets and long enough to tuck the ends under the mattress. Look on line they have products for this. Remember you aren't alone. I had my mother-in-law in our home for 7 years, last year I couldn't care for her because I couldn't lift her so had to put her where they could care for her, she couldn't even help when I bathed her, very hard but I'm 72 and have a bad back and knees. It is now my job to see that she is taken care of. I will keep you both in my prayers. My mother in law is 96.
Thoughts and prayers
Mia