Ok - I'll play "devil's advocate" here and say when you agree to ride with friends, you all must compromise if you want to ride together. That might mean stopping when you aren't ready or don't see the need. That might mean pushing the pace more than you want or going slower than you might normally do. It is about a "group" ride. My husband almost never stays with the group and does his own thing. I rode with two women a week ago Saturday and two other women a week ago Sunday. We all stayed together till the last few miles back into home base. I stopped way more than I wanted to or needed to but had chosen to be part of a group. I like riding like that. BUT... sometimes I prefer challenging myself and just do my own thing. Biking should be pleasurable for you so you should be able to do what you want. She should never have gotten upset that you didn't stop. But at that point, you chose to not be part of the group and that should be okay too. She should apologize for excessive venting!