My DD sees a pediatric Opthamologist because both of her eye's cross periodically. It is important to note that there are other interventions that you can try before surgery... glasses, patching and vision therapy. Some of them are not right for all cases, and are not as affective as surgery. But, there are risk and failure factors when it comes to surgery too.
Before you start to freak out, meet with the opthamologist. He'll be able to evaluate and identify what is best for your daughter.
Finally, I just want to say, even if your doctor does think your daughter will need surgery one day, it probably won't be until she is much older. My DD is almost 2 and her doctor is still talking about holding off on surgery. He reminds me, every six months, that as children grow, their eyesight improves... and it is possible that as Lily grows, she will grow out of her cross eyes.
P.S. My daughter was also a preemie, though admittedly much earlier than yours was. I just want to tell you to be careful this winter. Our first winter was a doozie. We were in the ER every month August through April, and we were admitted 3 times during that time.