Quoting C&M[PLM]:" she'll lose her supply if she does that."
That's nothing like certain. When I had my first, I followed an LC's advice to pump every two hours and wound up with a painful and awful case of oversupply, and so sleep-deprived that I was nearly hallucinating. When I had my daughter, every three hours, and an overnight break, was plenty. I really think that letting myself sleep 7-8 straight hours a night probably meant I had more milk, because I recovered from the birth, and the associated blood loss (dd was born early because of a placental hemorrhage), faster.
Obviously, the mom in question has to evaluate what's going on with her and her body. I do, however, feel that it's very important not to put so much emphasis on pumping that everything else (like kangarooing the baby and giving mom time, energy and resources to recover) suffers.
The NICU is a hard place to be, and there's an immense and necessary focus on the baby. But mothers need to come out of there healthy too. At the end of the NICU stay, you go home with, basically, a newborn. It's best not to already be sleep-deprived and undernourished at that point.