How long is a proper time to mourn my estranged husbands death?

Your story or his I should say is flat out really sad, I'm sorry about him ever going to Afghanistan and having suffered so much. I understand you did what you had to do and you did all that you could, I don't know if you have children or not with him, but imho a wedding where everyone there is bound to have known your husband and been sympathetic to his plight probably wasn't the best place to be socializing this soon. He was mentally ill he didn't choose to be that way, so people would probably see you as a wife that abandoned her husband when he had terminal cancer.. Mourn as long as you want but out of respect for his children friends and family, and his memory don't do it smack dab in front of the people that loved him too. Be discreet and respectful, many people lost him not just you. Pick up the book "how to survive the loss of a love" read it follow the steps and it will be your best companion at this time. take care