We are taking my daughters best friend on holiday and have decided that we can cover the full price of flights and accommodation for her. Her family are in slightly reduced circumstances and also have more than one child so money has been tighter for them recently than us. Its honestly going to mean more of a holiday for us to have her along. I just would like to let the mum know without making her feel embarrassed. Its been quite ambiguous until now, but If she's anything like me she will be silently worrying about the moment when I ask her for money. So far I've got "Hi XXXX, I just wanted to let you know that we're able to treat YYYY to this holiday so there is no need to reimburse us for flights etc. If you'd like to give her some money for souvenirs etc then I' sure that would be great".