I personally agree with what you did, though I too would have gone the additional step of letting co-worker know, as a previous poster stated. You were not necessarily doing it to get them in trouble but to get clarification in case the situation had changed, so that you could also take advantage of the opportunity.
As involves the cold atmosphere, instead of another e-mail, I'd do a personal contact with co-worker and explain that you were not doing this to cause problems but that you were hoping for a change in policy so you could also get OT upon occassion. Take her aside, let her know that you see how she might have construed your being involved as trying to cause problems, and then explain what you were doing. Ok, really you may have been trying to keep everyone on the same field and meant to kind of get them in trouble, but there's no need to tell her that and continue with hurt feelings in the office, so a little white lie, which really isn't since you did state you were hoping that then you could work OT too, could smooth things over.
Been there, done that, and it definitely helped the atmosphere. Otherwise, get a heavy coat, stick to your plans, and go about your day as if there wasn't a problem.
Either way, it's what you've decided and can live with.
CountriGal
Peer Moderator 
