Hey there, welcome.
I see a few people have mentioned already that there are a number of parents here who've got children with heart conditions and the like.
Let me also add that there are a few of us, including myself, who are adults that have had heart conditions all our lives, another great perspective that may help guide you through some of what your daughter's experiencing.
I was born in 1973 with a heart defect called transposition of the great vessels. Pretty hairy stuff, but I got better. =)
Everything kinda went south on me about three years ago and I ended up having my tricuspid valve replaced with an artificial one in 2003, been tickin' away happily ever since.
Please feel free to drop in any time, ask a thousand and one questions if you want to. We're all here to help eachother out and EVERYONE here has a different prespective on this stuff and LOTS Of valuable information and advice to share.
You can contact me any time you want through here or through my email which you can find by clicking on my handle, "Harpoon"
Take care, you and your daughter both. =)