Wow, lots more responses!
I feel I should make a few extra points of clarification, particularly in defence of Alice, who is - you know - one of my best friends!
1) I don't think Alice was being genuinely PA, which is to say I don't think she was trying to "punish" the rest of the group or set her own agenda. However, I do think that she was probably a little annoyed that nobody else seemed to be bothered about making a plan, and even when she noticed people were getting ready, she might have decided that she wasn't going to change her plans unless we told her that we had a start time in mind. However, it's equally possible that she thought that we were just getting ready for the day. As I said, we weren't standing there with coats and boots, we were for the most part lounging around on the sofa too.
2) Bob would definitely not have used "probably a couple of hours" to mean anything other than "probably two hours", but I think he probably meant to imply "because that's my guess for how long it will take us all to get ready".
3) Bob and Alice were the drivers, if that makes a difference. And Bob tends to be the de facto organiser on trips like this, which is why his voice would carry a little authority.
What I was interested in is whether or not Alice should have got up and ready when she noticed that other people were likely to be ready early, and it seems that most people do think that. However, should we have explained to Alice that we were planning on leaving as soon as everyone was ready, or do you think we were justified in letting our actions do the talking, so to speak?