Butterfly: the stroke for jerks!

Had a weird thing happen at practice today. I was finishing my swim with a set of 25yd butterfly to work on my stroke. I had the lane to myself, and for a time, both lanes to either side were empty. About midway through my set, an older woman got into the lane next to me and started swimming. Ordinarily I'd pay it no mind, but at one point when I was resting she turned to me and said "you know, it's really hard for me to swim backstroke when you're swimming like that, you're a real jerk!" When she began her statement, I thought she was going to make some kind of joking comment. But as she finished it, I realized she was serious, and it kinda caught me off guard. Since the lane on the other side was open, I moved over a lane so as not to disturb her, and tried to apologize when she was at the end of the lane, but she just curtly replied "fine" and went on about her swim. So my question is this, does swimming butterfly make me a jerk? I'm not going to stop swimming fly, but I'm just curious if anyone else has run afoul of other swimmers getting bent out of shape in this manner. To summarize, we both were in separate lanes (6ft wide), and she was swimming, not water walking. I wonder if Phelps runs into these problems :D