To become more comfortable, I suppose. She wanted her outside to look like what she felt inside, is the best I can describe!
Also, all of y'all saying "He" is "still a man" are being really disrespectful. Try to think- if you are a man, imagine if everybody relentlessly called you by she/her pronouns, and shoved feminine standards at you, and treated you as if you were a woman... and no matter what you said, they refused to listen insisting that you are female when you KNOW you are male? (reverse if you are a woman.)
Thats the transgender experience, asshole.