Francisco, biker shorts cost $150 dollars?? This store chick has serious game!! She was quite forward - did she put you in a head lock and force you to take her number?
I guess you didn't take the hint or maybe you are not attracted to her?
And "No", guys do not flirt -- flirting is wholly in the woman's domain to show a man that SHE will accept HIM if he advances!! Flirting is used as a reassurance mechanism on the woman's part and let's the guy know, "Yes, I'm available and I will accept your offer if you make one!"