I'm kind of torn.
I'm not a crunchy mama, but my youngest was only 17lbs at 1 year old and despite over supply issues, I could never pump more than half an ounce at a time. There's a difference between malnourishment and low-weight. If the little girl is meeting her milestones and developing at a normal rate, I'd lean more toward thinking she's just a lower weight due to genetics and only partly related to the raw diet (chances are, if momma's on a low-fat diet, her milk doesn't have as much fat as "normal" either, but the body pulls what it needs).
Honestly, when a doctor chewed me out for my youngest being underweight, I immediately sought a second opinion because I felt there was nothing wrong with her. Second doctor had no concerns and sure enough, other than some anemia (put her on vitamin drops and that was fixed 3 months later), my daughter was healthy.
Not sure what to do with your friend, but I would actually question what the doctor is saying, especially if he doesn't see the child often enough to have her growth chart to compare to.
Definitely all of this.
Pumping often does not expel the same amount of milk as natural breastfeeding would, so to pump and only get an ounce when you are an EBF isn't a surefire way to see how much your LO is actually getting.
My DS is tall and thin. Though he's over 2 1/2 years old, 2T pants do not fit him whatsoever. Like, ridiculously so; they will literally fall down when we put them on him. Even 24 months can be too big, depending on the brand, and we often have to roll them. However, he does go for wellness check ups and they weigh him/measure him anytime he is at the pedi for an illness. I was concerned about his size, and spoke with his pedi who showed me the growth chart. While he is thin, he has steadily been gaining weight and reaching milestones, which is ultimately what they are looking at. He is thin, yes, but he is certainly not malnourished and the doctor never mentioned that as a possible concern.
If your friend doesn't take her to wellness checks, then it's hard to determine, from a medical standpoint, if she has been gaining weight but just less frequently or at a slower pace, or if there was a point where her growth has started to decrease. They don't have all the information that they need in this case.