Oh yeah, my W is also on her phone using Facebook nonstop. Best you can do is fully ignore it. I think they are trying to get a rise out of us to validate we still care and they still have sway over our emotions. Don't even look over at her while she does it would be my advice.
I choose to be fully focused on my D and having fun whole she has her nose in her phone. If she chooses to not participate in that family time that's her loss.
Me39 M11 : T13 D9 BD 5/31/16 In House S until 6/21/17 Divorced 10/5/18