Girls do you avoid discussing your problems with guys you like?

I'm friends with this girl, and I'll always hear how she rants and vents to other ppl I know about what's bothering her and her whole life's drama/situation, but around me she's almost always nice, and I rarely see her angry or frustrated (even though they always do).

But when she comes up to me and starts a conversation I can tell when she's upset, so I'll ask, "what's wrong?" and she always goes, "I don't want to talk about it" and tries to change the subject to something else.

What idk is does she just like me less, trust me less, or is she trying to avoid looking bad around me, cuz if she doesn't like me idk why she comes up to me in the first place.