Your re-worded text was dripping in honey. Good, but I liked mine. Only because it showed you were trying to work with her, yet you were not going to let her be unreasonable with you at the same time.
Polite and detached is the key. You are under no obligation to make everything easy and give in to every demand. I love the:
"I know the kids need to spend time with you. How about sharing your schedule with me on Sundays just like you were doing a few weeks ago. That way I can set up our schedule to work in sync with yours. lmk."
And I think it is a foul for her to text your D6 instead of talking to you about Thursday. Lets just put a 6 year old girl in the middle because I can't be bothered to meet what are reasonable boundaries.
I would tell her so. No fair, foul, nix, nada, not going to be standard operating procedure. If you agree to this week it will happen every time and you will have the situation you said you didn't want.
And, dang it, give someone time to respond to you before you let fly for heavens sake. That's twice! I'll let you slide since you're a newbie, but I put less padding on the 2x4's if you repeat the same mistakes.
Me 45, H 46, S 23, M 26, Together 30, Bomb 6-2-08, S 6-19-08; H left 12-29-08. H home 12-09, Still MLC in 2012! Me- I have my big girl panties on. Bring it.