Girl at work who's really busy?

There's a girl i really like, who i sort of visit at her desk when i'm bored and i asked her to go to lunch (just the cafeteria downstairs). she's prettty busy so like 9 times out of 10 she turns me down, but i feel like she's legitimately busy and she makes time to check her callender and promptly responds to me. am i looking like a loser to continue asking her? i'm significantly less busy and usually am free for lunch. i try to play it off jokingly, and advice?