Hi,
I agree with Thunderbear, that your SIL has no business sending you nasty e-mails. When someone dies, it brings out the worst or the best in people. In your case it has brought out the worst. It's very common that the executor of a will gets the brunt of frustration do to jealous siblings. It brings up sibling rivalry all over again. Tell your SIL to butt out and tell your bro to speak up for himself. Hang in there and stay strong.