God damn I love this plug suit. It doesn't get better than this.

I can actually read that as, it is bitter, and she's teasing him about it. So the tone would be like "jyanai?"

Not 'it's not bitter' but 'is it not bitter'.

Yeah, that can work. Not sure of the intent, and my Japanese is still a tad basic.

now my japanese is really basic, but I thought it would have to be じゃないん. Did i just completely fuck that up? Im taking my japanese 2 final tomorrow...

The "jyanai" part is highly contextual. Depending on tone of voice, and other particles of speech, it could be a direct negator, or it could be a rhetorical affirmative.

Considering her character, and the situation, it's most likely the rhetorical affirmative.

itaitashii said:
now my japanese is really basic, but I thought it would have to be じゃないん.

That would be unusual. じゃないもん would have worked; じゃないの also, but not じゃないん.