A Little Bitter

So, my fiancé and I are expecting our first child together in just 8 short weeks. I have 3 from a previous marriage, he has one. Well since his mom found out we were expecting, she has probably thrown out there about 20 times that she's not babysitting. Here's the thing, my ex husband was in the military, I haven't lived near any family in about 15 years, I never had any help with my first 3, no daycare, babysitter, any of that. I let it slide the first few times she said it, then I let her know I didn't intend on asking her anyway, never had help with my other 3, don't expect any with this one. But yet she still says it any chance she gets, especially in front of other people, even cashiers at the store, etc. it's getting to the point my patience have run out for her unnecessary reminder. Should I just let her keep saying it or really just hurt her feelings with a response? Would you just ignore it? It makes me really care less and less about going out of my way to bring the baby by to visit or anything else after she's born. Too petty?