Antie Em receives so many questions that she can't answer them all. However, many girls had similar problems, so you might find the answer you need in the responses she wrote. She will respond to as many as she can. My friend is always telling lies. When ever something cool happens to me she always has to match it.
Some competitiveness can be a good thing.
A lot of successful people have competitive natures. But if she is constantly trying to out do you, she may be jealous or insecure. Insecurity is very common, but that doesn't make it any easier to deal with. Just try to be understanding and patient. Imagine how hard it would be if you felt like you could never measure up to her.