Need encouragement for a SAHM mom with 2 under 2 and caring for 82 year old grandma. How do I incorporate her needs and not become resentful?

So I'm a 29 year wife and mother to two little girls. One is 1 and the other almost 3. Me and my husband are living in a small two bedroom home. He was raised by his grandmother due to his parents being too irresponsible to raise him. So he has always considered his grandma his real mom. She did a great job and was so selfless in what she did for him. Now she has reached a point that she needs our help. She is in great health and just has her small moments of forgetting things, not understanding stuff, etc. So she has moved in with us. It has been about a month. We moved our girls into our room in order to provide her with her own privacy and space. She has a place where ahe can get away from the craziness and even has a T.V. in there. So basically I am happy she is here. Recently I have been struggling with being annoyed with things like, loss of privacy, things put in the wrong place, and having to take care of her more that I thought she would need. My two girls have been my priority until now, and at 18 months apart, they take up all of my time. How do I incorporate her needs now too, and not become resentful? I just want her to feel comfortable and happy. I don't know how to emotionally deal with this change. But I feel like a horrible person for being frustrated. Any help would be good. Thanks!