many questions about skin test results

Hello all, I got some bad news today. I have a 6 yo son who has been PA since 10 months old. I have just had my 3 1/2 yo daughter skin tested today for peanut, tree nut, and she tested quite positive to the peanut. I always had this feeling inside that she would not have this awful allergy. Boy was I wrong. She has never been exposed to any kind of peanut or nut in her life. My question is, how clear are these skin tests? My son was always blood tested. Her DR. suggested before the test that it is not likely for her to have the allergy just because brother does. He was just as shocked at the result. Her blister was quite big. He also, before the tests said we could oral challenge her in the office. But, once he saw her back, he said he didn't recommend it. He mentioned it could be a false positive, but it wasn't likely since her result was so strong. He wants to do the blood test now, and retest later to see if there is any drop in her levels. What do you all think? I know there is mixed opinions on the skin tests. I went in there today just figuring on getting the blood test. He then said since she has never been exposed, the skin test is more definitive. I am just so sad for her. The only good thing is that I am not going into this blind like I was with my son, but I just hate it for her. I really was hoping that one of my kids could just eat and not have to worry about everything that goes in her mouth. Please respond to anything you know about how your children and their siblings tests went. And also, anything you can tell me about the skin tests and their results on a child who has never been exposed, BTW, she tested negative to all Tree Nuts, except Brazil nuts. Thanks so much for any help you have. Amy