Mother in law insist on fresh food everyday

So my dear mil refuses to eat left over food. Every meal needs to be fresh cooked meal. She also doesn’t allow my husband or her grandchildren to eat leftover. It’s sibei fustrating for me. Cause what am I supposed to do with all these damn leftovers? She says leftover food is unhealthy and refrigerating /microwave will result in bacteria and this will result in long term illness. Hubby just listens to her when she’s home. Otherwise he himself loves leftovers. But he doesn’t think it’s worth fighting with his Ma about this.