I like skirts. My manager is fine with me breaking dress code to wear long skirts so I have reason to wear pants anymore. BFF told me tonight (at my place of employment) that if I marry a man who won't "let" me wear pants, she will not be part of my wedding. 17 years of friendship ending over pants. Not sure whether to laugh or cry.
Hang in there, PW. Despite your friend's jumping the gun on what your yet-to-have-met husband will or won't "let" you do, it does remind me that it is good that you're making these outward changes now while you don't have any men in your life that could be accused of influencing your behavior. Despite what she says, it is obvious that these things have to do with YOU alone and the decisions YOU are making. I'm sure she realizes that despite her initial frustration.
As crazy as it sounds, in her eyes, it's you that is ending your long friendship by becoming someone that she thinks she could never be friends with. Continue to be the friend you've always been within the bounds of Catholic standards and let her decide whether or not she can continue to be your friend.
ADD: If this friend is in any way an outright BAD influence -- presuring you to do things you shouldn't, etc -- it's a good idea to distance yourself.