There's very little drafting in our club's hill rides. Most of us could easily stay together as a flatland paceline, but we break up in the hills for the very reasons you describe. Even small differences in strength and gearing mean it's impossible to stay wheel to wheel on steep hills.

Back when I was racing, it was the same thing on club training rides. We had a flat course where we did pacelining, but on the hill courses we'd climb and descend singly or by twos, and regroup at the top of the longest hill.

Are you used to keeping a paceline going up and down the hills with other groups in your area? Does the one woman you've ridden with several times, ride with this group often? Why not check it out with her?

Many of the patch rides in Ohio attract people who really don't do any group riding outside of the events, and they're convinced that the way a paceline works is that the people from the back are supposed to guess (in no particular order) when it's their turn to pull, then power up to the front and take the point. They'll sit at the front and never peel off, and then sit at the food stops and the email lists complaining about "wheelsuckers." Maybe the woman you were on the hill with thought that's what was supposed to happen.

Or maybe the group has an informal agreement to stay single file when the traffic's that heavy. Actually just a couple of weeks ago our group did a new route that has a couple of miles on a fairly busy, 5-lane road. I would've thought it was perfectly safe to do a normal paceline with attention to the traffic behind, but the ride leader announced when we turned on to the road that there would be no leader change until we turned off it. The strongest one of us agreed to pull for the whole stretch.

In any event I don't think it's a big enough deal that you need to apologize before the next time you see these women. The next time you see the one woman you passed on the hill, you might want to just mention it to her.