Am I sticking my nose where it doesn't belong?

Complicated story, but here goes... A very close friend of mine (ex-boyfriend) is now married and has 3 kids. His only daughter (age 13) has curvature of the spine. I am not certain if this is causing her pain or not, but she seems to be a very active happy young girl. The thing that concerns me is that next month, this girl is expected to go under the knife for spinal fuson surgery. She will be required to be in the hospital for at least a week and will face several months of recovery and therapy afterward. She will even have to donate some of her own blood a month before the procedure in case she needs a transfusion. I know this is not my kid, but I'm worried sick about this. I wonder if this is even necessary. I'm scared that if I say anything, I'll look like the jealous ex-girlfriend who can't move on with my life. I just don't want anything to happen to this little girl. Should I keep quiet and hope for the best, or should I say something to my ex?