The only thing you even need to acknowledge right there is the tactical stuff. Decide how to split the bills fairly. And remember BE CAREFUL with texts and emails. It's a record that can be used against you. Obviously, keep this email, it works both ways.
Do NOT acknowledge any part of that email that was negative or mean. It's purpose was to hurt you. So don't let it.
Concentrate on the tactical stuff, make good fair decisions and purpose them to her. Do NOT acknowledge the rest. Throw her for a loop. Get her off balance. She's playing tough guy. You play neutral guy. Which in this case is the bigger person.
