She isn't suggesting taking 6 multivitamins a day is she? That can be dangerous, if nothing else completely unnessecary. About the only things you may need ontop of a good multi would be magnesuim and potassium. There are other suppliments for specific problems, you can research, but they may not be nessecary.
As for more fiber, remember you can subtract the fiber grams from your total carbs. The 20g net carbs is total carbs - fiber. If you are only getting 20 total, then you really need to up not only fiber, but your veggie intake.
As for 20g carb, no it isn't unhealthy. Our bodies can use keotenes for energy to the muscles and brain. We also convert some protien to gluclose, so it is still present in our bodies, even on limited carbs.
When you feel you are ready to move on from induction, just be sure to add carbs back in slowly and in the recomended order. Read
http://atkins.com/Archive/2001/12/15-381023.html which goes over, are you ready to move beyond induction.
Psyllium husks, and other fibers can help with both constapation and watery stools. She might also want to try cutting out all dairy for a day or two incase she has developed a lactose intolerence.