So I'm supposed to be driving up to London to meet up with an old friend over the weekend - coming back home Monday morning (about a 4 hour drive), I offered a friend a lift as she wanted to go to an exhibition in London. She was delighted and went ahead and paid for her entrance ticket and a cheap hotel room. Now the old friend would rather meet me the following weekend so I have told the friend I was giving the lift to that I can no longer help her out. She is a bit off with me - she's out of pocket for the ticket (non refundable and exhib is ending this weekend) & hotel as public transport is not possible and she has no car. Tbh I think I am perfectly entitled to suit myself - she is often strapped for cash and I try to help out when I can as I am comfortably off but I was doing her a favour in the first place so she should not be off with me. AIBU?