Akenside ... you may be feeling a little bruised by the advice given here, but it is well meant.
I would echo "Bluebelle", as have others.
There are a few things to reflect on:
AS a young DIL, I would have been terrified by the implications if my MIL had changed her job because I was having a baby. It does not sound as though this was a family decision, discussed and agreed on? can you see the assumptions made, about when and how often your help would be wanted?
I also thought that it would be nice to have my GC stay each week, to give parents a night off, so understand that thought process, but it is a parental choice not our choice. As it happens, DD had awful PND and I ended up helping a lot through the week and never doing sleepovers because she panicked when he was out of her sight. They stay regularly now....but thats 5 years down the line!
Your DIL may be gently trying to establish that you are a much loved part of the family but that it needs to be on their terms.
Thats normal!
Surely we are not too old to remember those first few weeks with a new first baby? no sleep, struggling to stay on top of the basics, painful stitches, hormone driven emotional rollercoaster.......we just needed time, and space.
The best visitors were the ones who waited for an invite, only stayed half an hour and left behind a cake, or a lasagna that you could just pop in the oven later. Above all, they were non-judgemental about whether the bed was made or the washing done.
You say that, in the short three weeks since this blessed little one has been in the world, they have visited you a few times! Given how upside down their world has become, this says a lot about them wanting you in their life.
Do try not to spoil that by trying to make things fit your own vision.
Adapt, and grow with them.