When Bella went to Mc to bring him the box with his stuff, she immediately said something wrong with Monica, Elaine had written to Mc that if he didn't immediately withdraw his stuff she would have thrown it in the garbage. Then having heard of the conditions of the will, he changed his mind and became very sweet with Mc and in the meantime seduced him, as Bella had already done.
I believe the mail was sent by a person who is not Monica and Elaine, both of whom are victims of the Mc Father's game.
Everything is played between Elaine, Monica, her daughters and Mc, to make the choice even more difficult.