What does it mean when my girlfriend says she doesn't feel like talking to anyone, but then...?

What does it mean when my girlfriend says she doesn't feel like talking to anyone, but then I see on twitter today that she was having a joking conversation on twitter with some guy? Last night, we were texting and after a while she stopped, I guess "carrying her weight," in the conversation (very short responses). I asked her a semi-important question and her reply was, "Idk." I told her that it matters to both of us and said that any input would help. To that, she said, "No thank you." After verifying that she was declining to provide input, I asked if something was wrong. She said, "I'm in an indifferent mood and don't feel like talking right now, to you or to anyone."

I told her that was fine and to text me when she was in a better mood and said good night. I don't usually get bothered when she needs her space, but between the fact that I still haven't heard back from her, and the fact that moments after saying what she said she was joking with some guy on twitter (didn't seem too "indifferent" to me). I suppose there could be a chance that she was merely putting on a facade because she didn't want anyone seeing her vulnerable, but at the same time I can't help but feel like she just didn't feel like talking to me specifically. Probably noteworthy as well, is that she had posted a picture of the two of them (herself and the guy she had the conversation with) the previous night. I had never seen or heard of this guy prior to the picture, but she assured me he's just a friend from class.

Fact is, I would sooner cure cancer than unravel the female psyche. So I figure that maybe some of you can help me piece this puzzle together.
What does it mean when my girlfriend says she doesn't feel like talking to anyone, but then...?
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