First of all, I am so, SO sorry for your loss.
Second, I wouldn't be at all surprised if your husband's reaction to this woman and her proposition is at least in part due to his own unresolved grief at the loss you two have suffered.
The woman is way out of line. There is no way she should be trying to get your husband or you involved in something so potentially life-changing so soon after another life-changing event. You need time to grieve and process and get back to a place in your life that you are okay with. Then, MAYBE, tell your husband that if he wants to discuss the possibility with you -and only you, to start- you can't promise you'll change your mind but you will listen. Only if you want to, of course.
Grief counseling should NOT include her unless it's beneficial to BOTH of you (obviously not the case here). If he wants to talk to her on his own perhaps that's his right, but I would see it as VERY dangerous given the rest of the situation. You absolutely have the right not to have her present, even if it means having to go to counseling on your own.
I wish you all the best in dealing with this incredibly emotional situation.
Pan Female, Hinge in a V between my mono (straight) husband, Monochrome and my poly (pan) partner, ThatGuyInBlack