She is a little young to be into a hard and fast routine, but I think you can urge her into a better routine. Mind you, my son did not sleep through the night until 12 months- so I may not be the greatest one to ask. But we did have him on a fairly good routine by 2 months. For the first month I let him demand feed to get an idea what his "natural" schedule was (if there was one). I then tried to start scheduling him because he was going to daycare at 6 weeks. He was naturally eating every 1 1/2- 2 hours and I wanted him consistently at 2 hours. So if he cried to eat before that, I would try to comfort him in other ways and only if he would not settle after 10 minutes I'd let him have a little suck (2-3 minutes) to get him to that 2 hour mark when I would let him full on feed. But nighttime was the bigger issue (since we all wanted to sleep!!!) He initially was eating almost every two hours at night- 11pm, 1am, 3:30am, 5:30am (roughly). Since this was only a rough schedule, the first two weeks were spent just making this a firm schedule- which meant a few nights of waking him up at 1 or 3:30 to eat (which was hard to make myself do). When he would wake up to feed, like Samantha, I would feed him, but not play with him (in fact, I usually dozed off while feeding him in the recliner). After he was done eating, if he did not fall back to sleep, I would place him back in his bed, refusing to entertain him. If he fussed and cried, I might pick him up and doze in the recliner again, but those were his only choices- lay in bed and play with himself or be held in half- sleeping mommy's arms. When it got to the point I was just too exhausted to do this any more, I decided to try and at least reduce the number of night feedings by changing the times to 11pm, 2am, 5:30am. [This is my adaptation of the cry it out method- which I just could not do]. The first night we fed him at 11 and my plan was that I would not feed him until 1:10. So when he woke up at 1 to eat, I went in, picked him up, comforted him, rocked him, but made him wait until 1:10 to eat. After a night or two of this, he did not wake until 1:10 to eat. So then I moved it to 1:20. At the same time I was moving back that 3:30 feeding by 10 minute increments. It took about 3 weeks, but I did get him on that night routine I wanted- I just wasn't able to break him of that one night time feed until he was a year old
Everything I have read about scheduling baby (vs demand feeding) involves either the cry it out method or a modified cry it out method. If she is on NO routine whatsoever, you need to start by getting her on an 'easy' routine. This may mean feeding her more often at first. So if she eats every 2 hours lets say, pick the times you want her to eat- and feed her at those times, whether she wants to or not. And if she tries to eat before that try and get her to wait (I do not believe in letting them fuss for more than 10 minutes at this age- so like I said, if she does not soothe after 10 minutes, I might give her just a little to tide her over and do the full feed at the designated time). Once you get her on that every-2-hour (or whatever you choose) routine and it is well established, then start extending the time in 10 minute increments (or longer if she lets you). Keep that schedule for at least a few days, then shift again. It's always easiest if you develop your plan around her natural schedule (if she has one). You mentioned she wakes at 6am ready to go- you have to keep in mind, you may never break her of this- she may just be an early riser. We were never able to mess with my son's 5:30 feeding- he was bound and determined to eat at that time. And to this day, he is still awake by 6am every morning (we consider ourselves thankful if he makes it to 7). We have even tried putting him to bed late hoping he would sleep in but sure enough, he still wakes up at 6 and is just cranky and impossible from a lack of sleep. So be realistic in your expectations of what you will be able to do with her schedule. And hang in there- I feel your pain!!!