Punkin, Yes, it hurts terribly, but you have to pick yourself up and not allow what they are doing to control your emotional state. We all have been right where you are today, i.e., the being replaced in the eyes of the public. The only way to get through this is to hold you head up high, back straight and continue being the best person that you are. People will begin to see what they are doing and will begin to form their own opinions in due time. You do not want to add to that mix as being a party to the break up. Allow them to hang themselves.
The ow has over stepped herself and the older children will get tired of her pushing herself on them. As for facebook, isn't there a way that your dil can block the ow's postings to her?
I hope that you are feeling better today. Please do not allow them to ruin your day. Keep the focus on you and your family.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.