If im in the 1% of naturally skinny women what is the healthy weight for my height 1, 82 ? its very hard for me to gain !

You decide: "ideal weight" is subscience and entertainment. A woman needs only a little bit of body fat sufficient to keep her hormones able to sustain the monthly cycle. Your best weight is what looks and feels right to you and allows you to take part successfully in the fitness activities that you enjoy. Most women would be very glad to find it "hard to gain". Stay fit & your body will stay right naturally.