DD has a friend that she has known since toddler group, she is 6 now and they go to different schools. We usually meet up at some point over school holidays, its not a particularly close friendship, shes a nice lady and the girls get on well. She sent me a text yesterday asking how half term was, i had just had some crap news (nothing serious) so just texted back was rubbish. Anyway, sent a text today saying be good to see her and her DD at some point and that she would be welcome to come down. To cut long story short she wasnt able to leave house but had another friend round to visit today who i know and would me and DD like to walk up as she is working the rest of the week. I said yes and that i would have a bit of lunch and walk up - quite a walk so i thought it would be good for DD. Anyway, told DD who was so excited and proceeded to paint a picture for her friend. not more than two minutes later did she phone me back and say, oh are you doing anything tomorrow, she knew i wasnt because i said originally did she want to meet then, but she had said she was working - but another friend had just texted and said she was at a loose end and was going to go up and visit so would i mind going up in the morning before she goes to work in the afternoon - i was so 
that i said yes ok, i'll see you in the morning and didnt really think about it. My DD was really upset as she was looking forward to seeing her friend.
my DP said that i would be mad to go and on reflection I agree with him, yes it would be nice for the DDs to see each other but i just feel a bit put out and if im honest im not that fussed about seeing her tomorrow. Would it be petty of me just to not pitch up or ring and say i can't make it.