I have so many problems with my mother, but this was definitely one issue.
My brother and sister don’t have children either, but she has always pressured me more, mainly because I have had several long-term relationships. My sister doesn’t really date, and my brother was single for a while, although he had one 2-year relationship more recently and is in another long-term relationship now.
She actually once said to me that me not wanting children makes her look like a bad mother. She does have narcissistic tendencies, so I guess it’s no surprise that she makes my choice about her. I asked my siblings and she has never said anything like that to them. She got so upset when I split with my ex because he wanted children and I didn’t, like she was hoping he’d pressure me into it. She’d barely see the child anyways as we live on different continents.
In the end, I would say think of it like this: it’s your life. You have to make the decisions that are best for you, not have a child because she wants you to. At the end of the day, is she going to be the one doing 3 AM feedings, dealing with health issues that could arise, managing a rebellious teenager, bearing the cost of it all – kids are not cheap. No, it’s on you. You don’t owe her grandchildren. I would tell her firmly that it is your decision and that the topic is no longer up for discussion.
With my mom there are larger issues, like I mention, and I really don’t have contact with her after one last, disastrous attempt to skype. When I got over 40, and had recently married someone who also doesn’t want kids, she seemed to finally realize that her pressure wasn’t going to work. Yours probably will with time too.