I think I offended a co-worker, was it bad to say what I did?

Its the same way where i live, most people here wear athletic pants a lot. So, no If i were you I would apologies just because you thought she was offended by it. It was not offensive, but if she is a valued co worker and a friend just apologies because you care about her feelings. Also, to make up for it maybe you could go shopping with her one day or have a girls day out.