I don't think 19% is low enough for concern though. Nurses say ridiculous things sometimes. I actually joke with my friends about it, I'll say something not credible and ridiculous and then say, "I'M A NURSE!".
But at the same time, like I said, i'm not really sure about fat percentages and where they are supposed to be so she could very well be right. I know that BMI is always the best indicator of healthy weights.
Yoga is very good.
Planning meals is a very very good start to a healthy diet.
Just remember that at least 50% of your grains should be whole wheat, 5 fruits and vegetables, and the rest of the food pyramid, and you should be good. And don't forget to allow yourself a treat once in a while, since you can clearly afford it.
Also, I would try to include some aerobic exercise. Walking, biking, jogging, spinning, dancing, aerobics, taeboe, whatever floats your boat.
This is general advice for someone of any weight, since the goal should always be health, rather than bringing the scale up or down. I only think that the focus should be stronger on weight itself when the person is dangerously underweight or morbidly obese. Otherwise, just be healthy and the rest will fall into place
Man, i've gone on another health rant. Oops.
(Oh, and if you are concerned about wanting to gain weight/increase body fat percentage, increasing healthy fats is best! Peanut butter, cheese, fish, etc.) The goal for weight gain is always more calories in than calories out. So if you're exercising, (which I would STILL recommend), then you just need to eat more calories than you are expending.