It's a song from Star's perspective, but with added irony. She is just now realizing that she has feelings for the boy who's been in front of her this whole time ("in the last place I thought you would be") Her unexpected love for her best friend is unwilling ("What could I do?") and has been only now been brought up seeing Marco in his suit at the top of the stairs ("'Til I saw you").
The next line, however, is painfully ironic. Marco is not "waiting for" Star, but Jackie instead.
The next (incomplete) verse transitions into Star's fantasy. If only Marco could notice her romantically ("And if I catch your eye") then Star would feel happy that he reciprocates her affection ("it feels like I could fly") and relieve her from the "lonely world" that she is currently in knowing that he loves someone else.
The song is incomplete, but it's appropriate in that sense because Star's inner conflict is not resolved. On the contrary, it's just beginning