Unhealthy MIL Rant

I just need to vent, guys. FYI, my husband and I do not have any kids. I am not pregnant. We are not trying to have a baby. We do have lots of friends who are very excited for us to have kids, and we do want to have them in the future. One friend offered to babysit for free when we have kids, which we found funny. We mentioned it to my in laws as a funny anecdote. My mother in law is now upset because if she can't babysit, she might as well not have any grandkids and we won't let her because she's not healthy and we're so terrible and we're not letting her see her grandkids. Keep in mind, these grandkids DO NOT EXIST YET! Anyway, so we of course said the plan is for me to stay home and not need a babysitter anyway, and even if she doesn't babysit, that doesn't at all mean she won't get to see them. Notice we didn't say she can babysit. I didn't want to outright agree, but it's true. She is really unhealthy. She can't bend over, can barely sit down and stand up on her own, has to lean on something to stand for more than a minute, often uses a cane, shakes uncontrollably sometimes, regularly comes close to passing out from diabetic issues, and gets very angry when her sugar drops. She has had numerous strokes and a heart attack. There is NO WAY she is babysitting! Don't get me wrong; I love that she wants to be present. I appreciate that she is willing to help. I would love for her to come hold the baby while I take care of the house or something. But she really just is not healthy. I don't trust her to take care of herself, let alone a baby. And I don't appreciate being told that I'm mean and hurtful because I don't jump at the chance to have her watch our (future!) kids. What do you think? Any advice? Thanks for letting me vent!