Dude, she had a miscarriage! You can't ever understand. She was using her body to carry your child, and she lost it. She feels like she failed as a woman and a potential mother. You may think shes acting insane, and maybe she is a lil bit but as a woman who has had a miscarriage myself it sounds to me like shes grieving and hurt that you're happy about it, and as much as she may say she doesn't want a kid because she don't want to go through that pain again, deep down she may think she needs to know whether she can have children or not. Shes vulnerable.
Just don't have sex, let her grieve and stop telling her it's better the kid is dead for financial reasons.. that won't make things any better.