Mom's neediness is driving us crazy!

My mom has dementia and lives with me and my family. When I am not in the room with her, making dinner, doing laundry, spending time with my kids, or any other personal responsibilities, she calls me in and asks me what I'm doing or says that she needs help. I'll tell her what I'm doing or ask her what she needs help with. She'll say she doesn't know what she needs. In the evening, when my family is home and requesting my time, she's calling me in every 5 minutes! Of course she doesn't remember calling me in 5 minutes prior. I'll spend 2 hours with her and then she doesn't want me to leave. But she lives with us, so I'm still present. Any suggestions? Thank you and God bless all of us who deal with the stress of caregiving!