jeannie I have in been a very similar situation and I wish I could offer some advice, sadly I have none to give but I do want to offer some support.
I have read on this thread some critical remarks and understand why you've felt the need to say that you "are not the m.i.l. from hell quite the opposite"; neither am I. I am confident that my other d.i.l. would agree with me and that she and my other son would also agree that like you "I am a support to all my family".
I still remember the look of resentment when I picked our grand child up at just a few weeks old and he stopped crying. If it had been his mother, father or grandfather who'd picked him up at that particular moment, the result would have been the same.
I still remember how shocked there's no other word for it, we both felt when he was happily laying on his play mat and his mother scooped him up and took him upstairs. When she came back down and handed him to my DH it was done so begrudgingly that the poor man gave him to me and then all he wanted to do was leave.
We can all I'm sure remember how we felt bringing our first born home and remember how invaluable the support of friends and family, including parents' in law, can be.
I hope this is a glitch and things will settle down so that your grandchild will be able to benefit from healthy, loving relationships from the entire family. It goes without saying that not all d's.i.l. are difficult to get along with and neither are all m's.i.l. To take a perfectly contented baby out of the room when grandparents are visiting and then not return is rude and unreasonable, and being a new mum isn't an excuse for either.
Congratulations on the birth of your grandchild