If when you open she does not seem to appreciate your approach and she looks annoyed, embarassed or whatever... how long do you try to insist before ejecting the set?
Of course you should give up at some point, but when in your opinion?
I remember one girl sitting on a bench that I opened directly by telling her she looked attractive. She told me that I could stay there next to her but to mind my own business in a quite rude way. I told her to pretend I did not say anything. After I while I told her the truth, which number she was that day, how many approaches I did until my first lay etc... and she instantly smiled back and got hooked to my story
Of course I lost all my credibility (that was my first "honest approach"), but I got instant comfort with her.
What I want to say is that sometimes there is a way to change her first impression of you also from the most discouraging start, but telling her the truth about pick up is probably not the best way if you really want to attract her and not just entertain her.
Are you persistent enough to try to attract her also from a bad start?