How much is she taking at that feed? If it's a substantial feed I would reduce it gradually, an oz at a time every three nights then resettle. If it's a small feed I would water it down gradually.
What you do at 6 am is up to you really, we treated everything before 6am as a nightwake but if they woke at 6 that was the start of the day - it's a pain, but I didn't feel it was worth the agro of resettling for the sake of an hour. It also meant I (or DH) could take her downstairs quietly so she didn't wake DS too early.
Laura