I'll echo what sparky said and take it one step further. Does she wear make up, anti-wrinkle cream, high fasion shoes or clothing? Is there anything that bothers her about herself? What if she lost some hair? Would she wear a wig? Think about getting a HT herself? People are often quick to critize w/o thinking about being in the "other persons shoes". If she can honestly answer ALL of these questions above with a NO then she is a better person than most but I have a feeling she cant.
My wife is exactly like yours but shes very contadicting. She thinks that anyone who tries to alter thier appearance is fake and insecure, but she wears make-up and puts on an acne mask every night. She also buys expensive purses like Coach. So what does that say about her??
Have you explained why you want the HT? Did you tell her because you wanted to look younger? Or because it would help you feel better about yourself? I find the latter excuse could be a little easier for our spouses to understand. Good Luck!!