I am sorry that you had this experience with your DIL on what should be the happiest day of their lives. She sounds like she has a very severe problem. I have a great deal of respect for you GmawMary, you sound like a very kind and considerate person. Be there for your son -- he is going to need you in the future.
Also, I have a BIL who I do not get along with. I have finally stopped trying to like him after almost 40 years and I finally feel like I am free! I still do not like him but the burden of trying to like him is now lifted and it feels good. I assume that you will have to do something similar with your DIL -- for your son's sake and your grandbaby's sake, I hope that you can do it -- it is not easy...