Hello,
Sorry for rubbish thread title, didn't know how to word it.
So, I'm going to an event which is roughly an hour's drive from where I live, in early December. I had pre-booked two slots as my mum wanted to go initially but now she cannot make it. Thats fine and not an issue. So yesterday I was having my hair done at the salon and the hairdresser (who I already know but not really well) were chatting and I mentioned this event I was going to and she said she was interested in this kind of thing and always wanted to go to it but she's not a confident driver and was put off by driving there on motorways in the evening. I said I had a spare slot going free if she wanted it, told her it's £25 (for the cost of us the event) and she said yes, fine. The payment isn't the issue. I told her we would need to leave for 5:45 pm, I would come and pick her up (she lives 2 streets away) and we would set off so we would be there in good time to find a parking space etc. (It starts at 7pm). It's a Friday evening we are going and I'm worried about being stuck in traffic and delayed etc. She suddenly hesitated and said that her husband wouldn't be home until 6:15 due to work so could we leave then? (So he could look after her DD). I said that I felt it would be a rush if we left it that late and I don't feel comfortable leaving at that time. I felt it was a cheek really to expect to change the time we leave as I'm willing to take her there, wasn't going to ask for anything to contribute to petrol or parking costs as in driving there myself anyway. Surely if you're having a free lift you don't dictate what time l?! Her childcare arrangements aren't my concern (I don't mean this to sound mean, I have DC myself so know how tricky it can be to try and coordinate this).
I really don't want to leave too late and risk arriving late. Now she is saying she will try and get someone to come and watch her DD so that we can go earlier. The thing is, if she can't make it I need to know so I can offer the spare place up to someone else. She says she will let me know nearer the time 
I am happy to take her and I know she is interested in this event but feel a bit awkward now as she clearly wasn't happy with leaving at the time I specified. How do I handle this whilst being kind and considerate as she is a nice person so I don't want to be mean!