K.C.
I had a friend go through this with her son when he was 7-8. Actually, they had no idea anything was wrong with him. But, his father and uncle both had heart problems that they determined were hereditary. They had the son checked out and he had it too. He had surgery over the summer to correct it. He recovered incredibly quickly with no ill side effects at all and is back to all of his regular activities. Happy and healthy.
The important thing for the mom was doing a lot of research into cardiologists and finding someone she was very, very comfortable with. The one she found had an excellent bedside manner with the son and was great at explaining things to the parents.
Of course, the entire thing was very nerve-racking and scary, but the doctor did help put her at ease and everything worked out really well.
I hope your daughter is ok!