Hey there, welcome to the forum. I have questions. Lots of them and I’m sorry if it’s a bit overwhelming but I just wanna get to know you and the situation a bit better.
How old are you? How long have you been roommates? How did you get thrown together with that person? Is there anything you have in common?

You say you want to be the opposite of what she describes but some of those things can’t be changed for example your height and the tone of your voice. Those things don’t define you either. I think the most important thing is how you genuinely see yourself, and learning to accept who you are. Maybe there are things you need to change to help with your self confidence but it can’t happen overnight. I have similar issues with my self esteem and thought I was doing really well with improving that before I had a huge set back a while ago. Confidence is such a fragile thing.