You called her? What for? You opened this can of worms. Things were relatively peaceful. Do you enjoy the upheaval she causes you? If someone makes you unhappy, it's very simple. AVOID THEM as much as possible. Don't call, don't write little notes, don't send emails, don't get together. Just do what you need to do at work to keep peace there and once you walk out the door at work, Sue no longer exists. If she calls you, be polite, but get off the phone really quickly. Tell her there's a pot boiling over on the stove and you have to hang up. Don't offer to call her back. If she writes or emails you, ignore it. Keep doing this and she will give it up eventually.

BTW, I just noticed you refer to her as your friend. This woman is not your friend. Never was, never will be. You need to find a new definition for "friend".