Girl acting weird from a compliment?

It wasn't anything overly suggestive or anything, and I consider us friends because we joke around and stuff.

But she was dressed very professionally today for some interviews around campus and when I saw her I said "wow look at you! you look very professional, you look great."

And she seemed weird and said that everyone was dressed this way for the interviews and it was no big deal.

The only history we have together is that a while back she had a crush on me and I sort of indirectly and implicitly rejected her, she disappeared for a while, and now she's hanging around again and we seem to be friends getting along okay. Why does she not take a compliment, can't friends compliment each other?
Girl acting weird from a compliment?
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