My mom wants a grandchild but I refused to give her one

It’s not about my mom, it’s about me and my decision of not having kids. My mom wants a grandchild more than anything else in this world. I can’t count for how many times she’s asked me if I have ever considered having kids. She even offered me to pay for all of the expenses and to babysit for me every time I need to go to work. I feel bad because the only thing she wants in this world is something I don’t want but at the same time I can’t give her a grandchild just because she wants it, I need to live for myself.