I honestly think that weight sounds perfectly fine especially since your daughter was premature. When my son was 1 yr he weighed about 17 lbs and he was 7 lbs 6 oz at birth and i think his weight is fine. The doc put him on pediasure though cuz it wouldnt hurt him to gain a little more and now hes 17 months and weighs about 23 which is pretty good. if ur concerned about her weight ask the doc about pediasure or maybe try to feed her more carbs, bananas, and yogurt which are high in calories and most kids like them.
I am the mom of a former 23weeker now 10yrs old. He was 1lb/1oz at birth. I remember back to those days like they were yesterday. I would talk to your doctor, but, if she is starting to walk and get around remember she will burn more calories. My son had some lingering issues with breathing (not bad) but still enough to burn a few more calories. We did have him on Pediasure for a while but it was costly. I found out from another Mom who's preemie was older about Carnation Instant Breakfast and discussed it with our Pediatrician. I took the box in so that we could check it together and it had everything that Pediasure did and he liked the taste better.
Here is my experience with liquid calories that I will share. Her weight sounds about right for a 24weeker, but that is between you and your doc to follow. What I found was for all the extra liquid calories I gave him, he (his body) adjusted how much solid food he took so it really wasn't a a huge calorie increase, but it did some. After a year I just had to learn not to worry about it so much, which was hard for me because like you I was worried and asked the exact same question you are asking. I started to try and focus more on making sure he wasn't loosing weight. He is still in the 3%-5% for weight for his age (54lbs) but that is just who he is.