Rude, or first in line?

I don't think anyone raised to follow the golden rule ("Do unto others as you would have them do unto you") would argue that common courtesy has taken some serious body blows in today's society, and sometimes seems to rank about as high on people's to-do lists as returning calls from telemarketers. But what do you do when you're actually not sure what common courtesy dictates you should do?

At the gym this evening (I know, I know, that whole winter runner thing...but it was dark and I haven't found a bright top yet and there are cyclists who yell at me if I'm not visible enough!), the elliptical crosstrainers were full when I got there, so I did some strength training first. Still no open ellipticals when I finished that, so I resigned myself to some time on a bike while I waited for one to open up. I saw one woman (let's call her Jane) start her cool-down, so I got off the bike and went to wait behind her machine as she got off to clean it.

As Jane was coming back, the woman on the machine next to her (we'll call her Sue) - another elliptical, but one without crosstraining capacity (nothing to work the arms) - stepped off and asked her, "Are you finished?" What? I was standing right there! I stepped forward as Jane responded that she was, thinking maybe I was outside Sue's peripheral vision. But no, Sue started to move her water bottle to Jane's recently vacated machine, so I stepped forward and said politely, "I'm sorry, but I was actually waiting for this machine. Were you waiting, too?" (Just for honesty's sake, I feel I should mention that my version of "polite" when I think someone may be wrong can become obnoxiously over-polite.)

Sue turned around and gave me that silent stare, humming with fury, that I usually reserve for people who cut me off and/or step on me on the Metro - for a full five seconds. Finally she said, "Well, so was I, but I guess you can have it," in a voice to match the stare. I set my water bottle (an anodyzed aluminum SIGG, from REI - no wasteful plastic or pesky BPAs here) in the machine's holder, but didn't climb on yet, saying, "Are you sure?" Sue didn't answer, or look at me.

So I'm stumped. Was Sue's claim on the coveted elliptical legitimate and her resultant fury righteous, or can I go back to the gym next time without having to hang my head in post-elliptical-usurping guilt and shame? I know one of us committed a common courtesy faux pas, but I'm not sure if it was me or her - what do you think?