Ha, I just watched Juno yesterday and was wondering, myself.
I figured her as ISTP. She reminds me of my ISTP best/f.. She seemed so Se go with the flow and doing whatever she felt like in the moment. "What is sexually active?!" reminds me of when I was onced asked "WTF does long term mean?" and other stuff regarding r/ships from my best/f z.z'
INTPs seem more oblivious about the world around them.. the way Juno would just grab furniture and not care that she was taking someone else's stuff. W/e about it. o_O Or she'd notice something, an object, and then enquire about it, such as Mark's guitar room. She didn't care she was in the middle of doing something, or maybe not care, but wasn't particularly aware that an important meeting was taking place? I would think an INTP would sit through the meeting as it's important, and they realise so, and get it over with, or am I wrong about that?
And her room...oh man !_! I wonder, would an INTPs place look similar?
Anyhoo, makes me think Ti then Se, rather than Ti then Ne. Yea, nemo, not INTP! No Ne Ti o_o Can't see her as an ENTP... I see ENTPs as playful with people, or will toy with them for fun, harmless or otherwise. And they seem to have energy !_! With their mouths... Juno wasn't a rambler. I mean.... Emotional restraint and intellectualizing of emotions, you say? ISTPs!!! Demonic Fi z.z She wasn't even aware that it's *iffy* to visit someone's husband alone, being as young as she was too. It didn't even occur to her why that might be bad... even when questioned, it was a "What? I don't get it." kind of reaction z.z
I didn't think of her as theorizing to improve her situation through the tons of possibilities either, more like she thought and then threw it out for someone else to deal with lol...