S.M.
If you're a doctoral student, you'll probably enjoy reading up on some research on infant and toddler sleep patterns. No matter how bizarre your child's sleep patterns are, you will be reassured, because it can be all over the map. Some will have very regular sleep patterns, some will consistently wake 3 times a night, some are sleeping 6 hours straight for months and then waking up a lot - it's not unusual or abnormal for them to have very erratic patterns well into toddlerhood, so don't worry too much about what you may need to do differently. Yes, some parents find that they *can* control their baby's sleep pattern to some extent, but for others it's just an exercise in frustration. Children WILL outgrow the need for nursing or comforting at 3am, even if you do NOTHING to discourage it. So I'd recommend to just go with the flow and not try to control things too much, but you do have to find a way to make it work so that everyone in the family gets enough sleep and the child's needs are met. (Mom deserves to sleep, too.)
http://www.kellymom.com/parenting/sleep/sleep.html
(Lots of info there, the most interesting is "What is normal when it comes to baby's sleep?")
Both of my kids woke up at least once a night until they were at least 2, although they would need varying degrees of comforting in going back to sleep. But even as an adult, I usually wake up at least once a night and have to get myself back to sleep, so maybe they get that from me.
When my first baby was about 6 months old, I woke up in the middle of the night to nurse him back to sleep, and I was sitting on the edge of my bed to keep myself awake. Well, I was so exhausted I started to crash and I woke up just in time to catch myself from falling to the floor with the baby sliding out of my arms. The next day I got a safety rail for my bed so I could lie down and nurse him and he would be safe even if I fell back asleep. (I NEEDED sleep badly then, and I wasn't about to do the whole "sleep training" thing. I needed to be able to wake up, put the kid next to me, shove a breast in his mouth and fall back to sleep or I would be lying awake for HOURS.)
And as far as the pediatrician telling you what your baby does or doesn't need, with all due respect, he/she is NOT the one having to wake up and deal with the baby at 3am.
If your baby is telling you she needs to nurse or be comforted, do what you need to do to get everyone back to sleep. The pediatrician has no say in how you deal with your baby's nighttime needs unless you approach him/her saying it's a problem.
I heard a similar argument from my pediatrician when my youngest hit about 12 months. (we weren't having any problems, she had just been asking about night waking and how we handled it.) I said, yeah, sometimes he wakes up, but I nurse him back to sleep with no problem. Then she kept insisting "He doesn't NEED to nurse" and "you DON'T need to do that." (The subtext was "so stop doing it"). But notice who has to deal with the crying - not her.
And finally I just said, "Look, this works for my family. If it stops working, I'll research sleep disorders and get the help we need." And that was the end of that.
Good luck!