hmmn....this comes down to being assertive and when I was at work the hardest thing for women of our age to do - say 'no', just 'no' when we don't want to do something. Our company had to put on special women only training (another fault is being timid in asking for something for ourselves, eg pay increase hence the disparity which I believe is around 18% in men's favour to date?). We always add a clause in mitigation or fib for fear of offending, looking mean etc etc. It's hugely liberating and I so admire a friend who was very senior in a £multi million corporation who can do it briskly, with a smile and no one takes offence. She closes any avenue for someone to come back. In this case I'd just say, thanks for the suggestion but the offer was for you only. If you wish to reschedule a date let me know. End of.