Her lactation nurse is nuts. Maybe she means that 2 days is too early for your sister's milk to come in. Mine took 2 weeks, and I had to get some help to force it. Until then, my milk was very low in volume and my baby was nursing a LOT to get very minimal amounts of nutrition. If your sister did not rent a hospital grade pump, remedy that fact pronto! Those pumps are extra powerful and can get the most efficient suction. Another option for women whose breasts don't respond to electric pumps like the big hospital grades or the smaller at home electric pumps like the medela is the avent hand pump. I actually got a lot more milk from that smaller hand pump than with the big expensive electric ones, but buying all this stuff is pricey, so renting it from the hospital first to see what works is the best bet.
There are two drugs they discuss for increasing lactation, reglan and domperidone. Domperidone can be purchased outside of the USA, and reglan can be prescribed by the pediatrician or the PCP. Reglan has a history of exacerbating any PPD issues in a depressed mom.
Fenugreek is the herb that people talk about that makes your milk come in. It did not work for mine, I was taking so much I smelled like maple syrup. No joke. I couldn't eat pancakes for weeks after I started taking it.
I talked to the LCNP, she recommended dom and told me to buy it through canada or the UK with a prescription, and/or to start off with reglan right away. This was after 2 weeks of diligently pumping and nursing with not much volume coming out. I only managed to pump 4 oz at a time on a good day, with meds, so I know whereof I speak.
I also know that babies are getting more milk out of their moms than a pump can, weighing the baby before and after a nursing session can help calm a mom who thinks nothing is coming out.
But there are definitely some people who just do not make enough milk, and yes, there are options for them.
Reglan and Domperidone are both drugs that help empty the stomachs, domperidone was created for nicu babies in the hospital. They just happen to increase lactation hormones too, but are not "made" for that purpose, it's just a well known fact in the medical communities. If it ends up in breastmilk, it's not as big a problem as massive doses of some herbs.
Once her milk is established and she is nursing/pumping routinely, she won't need to take it anymore.
It took me 2-3 weeks to get on a med program and get my milk to come in, and now, almost 3 years later, I am still able to express milk. Losing weight also helped me for some weird reason. My diabetic overweight cousin never had her milk come in at all, but she didn't want to breastfeed, so for her she welcomed that. I fought my apparent genetic lack of lactation to the death, and now it won't end!
Anyone reading: if you have advice to make you breasts quit lactating, that would be awesome. I'll take an herb even.
Good luck!!!