What do you say?

A couple of weeks ago I stopped by the health food store to pick up some study treats (coconut curry, dried mangoes, fresh peanut butter, and a few honey toffees), when I saw the sweetest, most beloved young lady from church. She graduated, her mother re-married and moved away, and I hadn't seen her in quite a while. As I expressed how happy I was to see her, I noticed she had obtained eyelash extensions. They were very pretty, but I wasn't sure whether I should say something about them or not.

As one who frankly doesn't understand physical alteration, I place this question out there (and perhaps my beloved young friend will even jump in and help me out!). What do you say when someone alters his or her appearance? In this situation, I would assume that the phrase, "My, what big and beautiful eyelashes you have!" would be appropriate, however, there would be some circumstances where that would not be the right thing to say. What if that person is just trying to make it look like it is natural, and doesn't REALLY want you to say anything. Do you risk hurting their pride by noticing, or do you risk hurting their feelings if you act like you didn't notice?

I do not post this question with any malintent, just with a sincere interest in the answer. Aside from adding a few highlights to my hair, I have never considered changing anything about my physical appearance. For my wedding I got acrylic nails, and immediately soaked them off with acetone afterwards. I couldn't stand the feeling of big fat fake nails on my hands. That's not to say that they don't look nice on other people, just not on me. What do you think? Say something or not?