I would have just contacted her and said sorry busy this weekend, contact me next week and we'll see if we can organise something for the weekend after.
Why do you need to call her tonight to discuss it? That's extra contact that isn't necessary IMO.
H 34, W 36 T 13.5 M 8.5 C 6yo twins S 6/5/11 OW 7/6/11 OW moves in 9/18/11