I was going to say kind of what Therese said but probably not as eloquently. I did the best I could with nursing and pumping for all three of mine, and I still feel a little bit guilty from time to time that they weren’t exclusivley breast fed for at least a year. And I still feel badly about the fact that had I know certain things about breast feeding and infant reflux back then, I would have done things differently and my babies probably would have been breast fed or at least been fed pumped breast milk even longer than they had been.
Now getting back to what Therese said……I’m fortunate that no one criticized me about not breast feeding or not pumping for a year, but I still felt guilty, sad, disappointed etc because it was so important to me to breast feed and I wasn’t able to do that. I guess what I’m trying to say is that what your mil said is inexcusable to say the least, but my guess is that you are going to grieve and feel some guilt no matter what anyone says or doesn’t say because the breast feeding means so much to you, like it did to me. Just like anything else that you grieve, it gets better with time. I still feel a little sad when I think back on it, but back when my supply was diminishing, or when I gave up pumping, or when I realized my babies were not going to nurse, the grief I felt was very strong. I know it is for you too right now. I remember how much it hurt. 
But try to remember that you did everything you could and your baby did get six months of mother’s milk, and she will get a lifetime of motherly love. 
