First of all, I am very sorry to hear that you lost your sister/best friend to CF. The only thing about losing someone to CF is that you know that the IV's, hospitilazations, feeling badly, etc are all over with for them & that they are cured. That doesn't take away your pain, but it helped me cope with losing my sister years ago. She was ready to go! Hang in there.<img src="i/expressions/face-icon-small-confused.gif" border="0">
I would defininately get re-tested by a CF doctor/Center. They can administer the test the best since they are familiar with the proper technique. Sometimes you can get false negative sweat tests, so just to rule this out and/or to get answers, I would have one done.
You could also just be extra sensitive right now too with the loss of your sister, but I think this health issue being up in the air isn't helping either, possibly adding a little more stress. Knowing one way or the other will relieve some of the worrying.
If you do have the test done, let us know how it comes out. God Bless