Mother in law

Just want to rant. My mil promised to take care of my 3 months old baby for a month. However after she realized my husband also took leave to stay at home for the baby, she keeps saying why need 2 people to take care of the baby and always disappear in the afternoons and leave my husband alone with the baby. I know some dads are excellent baby caretakers but my husband is not one of them, he’s still clumpsy and a little bit scared. He has to beg his own mother to stay and help everyday although she already promised to. When she stays, she complains about the way I take care of baby, saying I’m ma fan and overly concerned. We are always very polite towards her and my husband still gives her 600 monthly allowance (not saying that she has to help because of the money). A promise is a promise, especially to loved ones, isn’t it. I just don’t know how to face this kind of irresponsible grandmother..