I think the trick really is just going to bed earlier yourself (so you cope better with the lack of sleep), responding as quickly as you can (because sometimes they will go back to sleep if they don't wake too fully) and just riding it out. We co-slept (but even when she moved into her own room and would come into us very early), about 50% of the time I could get her to go back to sleep in bed with us and I'd get an extra hour of sleep. That helped. But I don't think there is a magic solution. It will come and go over the years and it's not just a baby thing. My 4 year old goes through spells of getting up at 5am still. She'll craw into bed with us sometimes and will lie with us (while we a little bit doze rather than actually sleep), or sometimes she'll play a bit in her room and give us an extra 30 minutes, often after waking us up very grumpy and tired to be awake so early. But going to bed earlier (you, not her) does help a lot when it's night after night of it. I often think it's due to something developmental going on or big changes or just something being a bit off, but sometimes there's no obvious explanation.