Girl sitting next to me in library, interest or random choice?

I study in the same library Mon-Fri. A girl started consistently sitting one seat away from me, even when the room was empty.

We had frequent eye contact before even sitting 1 seat away.

Eventually, I suggested she sit next to me for better access to the charger plug, but again, everyday there where plenty seats available with same plugs/chairs/view BUT distanced from me.

She agreed, and for 3 weeks we sat side-by-side.

We had very little verbal interaction (she politely declined gum in 2 different days), but I was curious about her, we never talked outside, I always felt shy, I don't know about her, despite crossing paths multiple times.

To test if she was actually interested or just using the seat, I asked her on a Friday if she wanted to join me at my library on Saturday, more specifically "Should I keep the seat for you at ""library name"" tomorrow?" (requiring her to change her routine, because we went to different libraries on weekends since the other 1 was closed).

I expected a rejection so I could move on, literally anything, like ""no thanks"" // "No I'll go to another library" // ""No I can't""... again, anything, I was ready for such replies.

To my shock, she said to keep her the place, so I said "okay!".

The Turning Point:

Right after agreeing, I went to the bathroom. When I returned, she had spoken to her best friend and changed her mind, stating she would go to her usual library instead. I asked her for details about her library (location/time) and she replied precisely, but then I just said "have a nice evening" and left without confirming if I would join her.

The Aftermath:

On Monday, she didn't return to our usual spot. She moved seats completely and distanced herself from me. Now, there is awkward tension when we cross paths.

Does she think I got offended by her changing her mind?
Was she expecting me to follow her to her library as a test?
Was she never interested, despite sitting with me for weeks?

Girls... what do you think?

Girl sitting next to me in library, interest or random choice?
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