"She has great hair!" (if you only knew.....)

Sam has great hair. It's long and thick and has body....she did NOT get it from me. It's kind of funny because as a baby she had rubbed it off completely bald in the back.  Anyway, she gets compliments on her hair from strangers. On the surface this seems nice, but inside it sometimes feels like a knife in my heart.  Generally when it happens it goes something like this:

A nice mom/grandma says: "She has beautiful hair! How old is she?"

Me: "Thank you. She's 3 1/2."

The mom/grandma lady: "Oh, my daughter/granddaughter is 3 and she hardly has any hair. I'm SO jealous!"

Me:  "Thank you." (smile)

But what I'm thinking is:  "If you only knew. I bet your daughter/granddaughter speaks. I bet she says "mommy"/"grandma" and gives you hugs and wants you to read books to her. I bet she loves the Disney Princesses and plays with baby dolls. My daughter doesn't do any of that. She can't even speak. I'm so jealous."

But of course I don't say that.  They're just being nice...they're giving her a compliment.  And compliments are good, right? So I just smile and say "thank you" and then I might get in my car and cry.  If they only knew.....