Does it sound like this girl is into me? If not, what is it? Why the bitterness? Please, I know it's long...?

Sounds like your obsessing over details and looking for signals and signs all of the time. She may like you she may not but sounds like she had other things on her mind that day. To answer your question what do i do now? - nothing act as normal be pleasant and polite but don't go out of your way. Let her make the next move then you will know.