Since she’s not staying with you guys, it’s easier. When you breastfeed, just lock the door. When she lectures, just continue to do your own thing without responding, overtime she will get tired.
If she keeps buying stuffs that you don’t need/like, throw it infront of her. It’s because she knows you won’t rebute her that’s why she’s going more and more overboard (nice to bully).
Usually the husband will be sandwiched but in this situation, his role is very crucial and he should be the one standing up and be stern to his own mother. If he doesn’t control his mum, the outcome is angry mother and angry wife. I believe most dils know how to 做人, if mil don’t tackle us, we also be nice. Putting filial piety aside, once married, YOU and baby are his family/priority, not his mum.
At the same time, you need to stand up and speak up for yourself too. Be blunt, be harsh if you need to. My mil used to be damn demanding until I lashed it out at her then she became tamed else she thinks I don’t have limit.