Nasty comments from MIL after mc

So we sadly lost our little baby at 10 weeks and since then, both of us have had a hard time coming to terms with it. We love and support each other and this loss has bonded us in a way we never thought was possible. The problem came when he told his mother, and she's never been the most emotionally supportive woman. She instantly started to point the finger.. 'Oh maybe it was your sperm that caused this, or her egg may have been dodgey' 'this was meant to be my first grandchild' and started crying for her self!! No concern for what we are going through! In no way was our loss our fault!! We ate healthy, exercised, drank water, and my tests came back totally normal and healthy! We did everything we possibly could to keep ourselves and the baby healthy, these things just happen and it's awful. But it doesn't matter what we say to her, she has her views on it. 
I'm absolutely distraught that she could be so cruel when her own son and I are finding it so hard to deal with the loss of our baby 😢 I have no idea what to do, I can't vent to my partner because he gets upset if I bad mouth his mother (but I think after this, I have a right to be upset with her) I just wish he would stand up to her for what she's said!
Sorry for the rant