I don't the hairstyle is the issue. As others have pointed out, the underlying issue seems to be a lack of a sense of self. Wanting to be "twins" with your T and copying her hairstyle suggests that you still have some work to do in figuring out who you are, what your style is, and developing a sense of self-confidence. There is a phase a lot of young girls go through where they want to look "just like" their best friends, and that's a normal part of development, but that's also something they outgrow when they get older and develop a stronger sense of self.

The other part of your post that struck me was the emphasis you put on being attractive to men. It seems that you're viewing your hairstyle as a way to relate to T and/or attract men, rather than as a way to express YOURSELF. Personally, I view my hairstyle as a means of self-expression-- I don't care who I may look like or who may find my hairstyle attractive. That's irrelevant. I want someone to be interested in me for who I am (personality, appearance, intelligence, etc)-- I would never change an aspect of myself or my appearance in order to be more similar to or attractive to someone else. If I did, then it wouldn't be "me" who they were attracted to in the first place.

I also think you're focusing here on a superficial element of similarity and attraction. Sure, you can have a haircut that is like someone else, but that doesn't actually mean anything. It doesn't make you any more like that person than you were before you changed your hairstyle. If anything, if the person you're emulating has a strong sense of self, then by copying her, you're showing that you don't have the kind of self-concept that she does. Similarity lies much more on the inside than it does on the outside. Same with attraction. I think most people would tell you that physical appearance has little to do with real attraction. The people who receive the most interest are the people who have the most confidence, vibrance, and unique characteristics. People are attracted to those who stand out as being their own person. Is T's confidence one of the things about her that you find compelling? Is it her hairstyle you really admire or who she is as a person?

The difference you've noticed (less attention) since changing your hairstyle may also be due to the fact that you're trying to put someone else's hairstyle on your face/body and, often, that doesn't always end up looking right. Have you seen pictures of those people who try to have celebrity hairstyles? They sometimes come out looking "off." Even back when I had a close friend who copied my hairstyle and clothes, something about it just didn't look right on her. Why? Because she was trying to be someone she was not. She looked much better a couple of years later when she figured out who she was and developed her own sense of style.