It looked to me as if neither of them was actually pushing it - one of those moments where we are supposed to look back and say "What if?"
The implication was that it was Lavinia speaking from beyond the grave about Mary and Matthew.
The above commenter is right - it's supposed to be Lavinia, giving her well-wishes to Matthew and Mary. "May they be happy. With my [Lavinia] love".
No - it's meant to be Lavinia. Richard Carlisle says that she mentioned that she knew Matthew wasn't admitting that he was still in love with Mary. It's her way of showing that she bore them no ill will.
I had the inclination that it was Anna pushing it, hoping that she could force Vera to bless the union. There's a bit of uncertainty in the delivery of Anna's lines between her and Daisy.
Vera would curse Anna and Bates from hell if she could; it's implied to be Lavinia, and, given her recent death, is probably her.
What do you think?