How to I tell my MIL to back off? (nicely)?

After a year or more of praying and budgeting and saving, my husband and I have made the decision for me to quit my job and be a stay-at-home mama. We are financially secure and can easily make it on one salary, although we will be making a few cuts in certain areas. He and I are thrilled, and the kids are so happy to have Mom at home now. The rest of our family is in full support, but his mom called today and just chewed his ear about how upset she was that I was quitting. Some of her reasoning: "There are people out there just dying for a good job, and you would just walk away from yours?" also, "What are you going to do for insurance?" Oh and my favorite, "Dad and I are going to be the ones who are responsible for bailing you out." Certainly as a mom she'd have a right to be concerned if we were making a flippant decision, but we've thought this through carefully for a long time and it is clearly the right thing to do. We've got the insurance thing nailed down, and as far as the people who are dying for jobs well guess what? One just opened up-mine! That's like telling my kids they had better eat their food because of the starving kids in India. As if our situation relates to the other. And yes, my hubby has borrowed money from them in the past but it has been paid in full for a long time now. And we've made it clear to her that I'm not going to be sitting around eating bonbons...we have 3 kids so I am definitely going to be plenty busy. Anyway my question is has anyone been in the situation of a parent's total disapproval and how do you deal with it respectfully? Moreover, how do you forgive and get on with life and not let the naysayer bring you down? Stay at home moms, how do you deal with the people who think less of you not having a "real" job?