My son had surgery when he was a baby, too. To my surprise, he has briefly addressed the issue with some of his close friends. He doesn't usually tell them the name of his heart defect -- just that he's had two open-heart surgeries and he has to be careful about certain things.
The fact that your friend is playing sports is a good sign. That must mean her heart is strong and so is her spirit. What I have seen with my son is that he wants to be treated just like any other kid. He doesn't want to focus on his heart defect or the fact that there is anything wrong with him.
If your friend had her surgery when she was a baby, there is scar tissue covering the wires in her chest. I doubt it hurt her when you touched her; it probably embarrassed her a little. Just take it in stride and try to be understanding. Some women are very concerned about how their scars look. It makes some women feel less beautiful.
I think that you're a dear friend for caring so much. Hang in there and enjoy whatever time you have together. Time really passes too quickly. We all need to cherish each and every day.
I hope you had a merry Christmas and I hope your new year is filled with joy.
mom to Joey (heart healthy; 15) and Alex (HLHS; 12)