So why do i get so upset when she tells me these things?
It's like I can't tell where I end and she begins.
That's what empathy feels like.
If you're maybe a little bit more self aware and you've got a little bit more of a clue as to the true source, emotionally speaking, of her behavior, then you're going to feel shitty if her behavior is rooted in feelings of deficiency and you're sensing that.
For example, a behavior that feels to her like validation may feel to you like abasement. Whereas she thinks she's winning at life, you may feel like she's destroying herself. What makes you feel bad may make her feel elevated.
If you're someone who has a sense of the inner values of life then you'll probably be bothered by people who compromise or ignore those values. You'll see her behavior as a problem because for you to engage in those same behaviors would maybe feel like a problem to you.
You'd be feeling those emotional factors underlying the actions, whereas she may not.
I just don't understand why I judge her. I do it with everyone to an extent.
Judgment can sometimes be a means of creating space and getting distance from other people's emotional debris. If you're empathetic and you have weak self/other boundaries, you're going to feel like you're pulling in other people's emotions all the time. Like you've got other people's emotional junk bouncing around in your system. By judging it, you can keep it at arm's length.
If you ever feel the need to tell her how you feel, you can do it without judging her. Read up on I-messages:
If you take the time to get clarity on how you feel and you can put it into words, you can know that everything you say to her is true and without judgment.
She may still feel judged or she'll disagree with your perceptions or she may question your interpretations of events, but if you stick to what you know to be absolutely true for you (when you... I feel...), then you can know you've spoken no falsehood and you have not judged her.
Speaking the truth doesn't mean she'll appreciate it or agree with it or accept it, but nonetheless, sometimes it demands to be spoken.