What Bokonon said is true, they worry about them expending too many calories and such. However, for us, it was a bad practice.
My ds was a 32w 6dayer and lost weight in the NICU for quite a bit. He was moved to the step down nursery at 2 weeks old and finally started to gain, but very slowly. I finally took him home (AMA) at 4 weeks old. He'd only gained a few ounces over his birth weight there.
Once we were home, I did exactly what you are talking about. I let him eat when he wanted and how much he wanted. I didn't push it, although I would wake him up if he was out for a 3 hour stretch (except at night-I have 3 other kids so when he was out at night, I was too!). I also took out the supplemental formula they'd been giving him and the vitamins. Luckily I have an awsome pediatrician and she had told me I could do all this and just bring him in in a week for a weigh. Beyond that I just took him to check whenever I got worried.
Concidering the age at which she was born, I wouldn't be so worried about her using too many calories. She either was or was very close to full term. I don't know why you couldn't treat her more like a typical baby-although I wouldn't be surprised if she's extra sleepy the first few weeks. I can't really explain why, but my son woke up much more often once he was home...it might've been all the noise around her or something, or maybe that I held him ALL the time at first and anytime I had to move to get somethng, it'd wake him up.
Anyway, the result of this was him gaining almost 4 pounds over the next month.
Obviously for him it didn't hurt. The thing to remember though is that every baby is different. While it worked for my son, it doesn't mean it would for you.
What if you took her home AMA and then she started losing or still wasn't gaining? Could you bring yourself to take her back to the hospital? Is there a closer hospital to you with a less intensive nursery? It doesn't sound like she needs the full out NICU anymore. That might be a good alternative-ask about her being transfered. Can you stay at the hospital? I know every hospital is different, but both of the hospitals I had NICU baby's at had some option-the first had a teensy room for me to stay in and the second had private rooms, so I had my own giant room with the baby, lol. I'm just wondering if her feeds would increase if you could be kangaroo caring for her.
Oh btw, when my ds was sent home, he was only intaking 75mL's every 3 hours. They said this was normal...he was also close in weight to yours (4lbs 13oz at birth, 5lbs something when sent home, I can't remember anymore!).