A couple years back, I had a relation with this girl. At the time, she was ~17 and I was ~19 years old. It was a sunny day and we were out having a drink. All of the sudden, she tells me how much she needs me, and asks me if I need her.

The word 'need' comes from 'necessity', which is something "absolutely essential". I need oxygen, water, etc.; I don't need people. I obviously knew what was about to happen, but I like being straightforward, so I told her: "No, I don't need you. I like spending time with you, otherwise I wouldn't be with you, but I don't need you." Of course she gets mad, I wasn't expecting my rationality to work.

The main question is: Why did she ask that, and what was she hoping/expecting to hear? Just in advance: I'm 99% sure she'd have acted worse if I had just replied with a short "no", and I'm also convinced she genuinely believed she wanted me to say "of course I need you", so I wonder whether she actually wanted that, or it's some kind of "unconscious" shit-test.