Personally I think the middle paragraph will come across as sarcastic. The last sentence of that paragraph IS making her feel guilty about it.
I would be tempted to go more with
Unfortunately you haven't given me enough warning to change my plans now. I realise that means you wont get to see D6 on her birthday but the offer for friday remains. If you cannot make friday then I'm sure you will be able to do something with D6 to celebrate on your week.
If she argues then reply with a simple
I'm sorry you feel that way but I made plans that reflect the situation we are now in.
In truth you probably need wonka about now though.
Both mid 30s, 2 young kids BD 7sep14 XW moved on long ago, now living with OM1 D paperwork in progress
