User02 When mothers stayed in hospital for 10 days after the birth, they were resting, had time (and the help) to get to grips with feeding, establishing the bonds, etc, etc. Visitors had to stick to set times so it was perfectly manageable.
These days, mothers get chucked out with little time to rest, have no help in feeding at home, and have to do all the feeding, establishing the bond, etc, at home. In the best cases, this is with supportive family, who, while visiting at sensible times, don't overstay their welcome, who don't plonk their arses down and expect a new, exhausted mother to rush around hosting while monopolising the baby, who don't expect the new mum to be available at all times so they can see the baby when they want, etc, etc
We've seen terrible stories on here about parents and inlaws (no discrimination from me) who have really caused problems by their selfish behaviour after the birth.
I'm not saying this is the case here, but given that the MIL booked leave without discussion with OP/OP's DH, I'd be wary of her motives, at least.