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A girl who already has a boyfriend kisses another.
-What about Whitney?(The girl's boyfriend)
-Forget Whitney. I've had my eye on you,
just like you've had your eye on me.
Is the underlined the same as
"I've always had a crush on you"?
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Not exactly, but in this context, it's close.

More like, "I've been thinking that you were a good choice for me."

You can use it as a good candidate for a job instead of as a boyfriend, so that's why "a crush" isn't right.
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.
Roughly the same, yes.