A blond suspects her boyfriend of cheating on her, so she goes out and buys a gun. She goes to his apartment unexpectedly and when she opens the door she finds him in the arms of a redhead.

Well, the blond is really angry. She opens her purse to take out the gun, and as she does so, she is overcome with grief. She takes the gun and puts it to her head. The boyfriend yells:
"No, honey, don't do it!!!"

The blonde replies:
"Shut up, you're next!"

This girl may not be as dense as she comes across. Let me clarify:

She had the notion to go and buy a gun and made a plan to barge in on her boyfriend, when he least expected it. Pretty clever, I would say.

She also was wise enough, to buy the gun at a store where either no one had ever heard of ignorant blonds and knew not to sell them one, or... she picked out a gun shop where the seller was a blond as well.

In other words, don't underestimate a person, just because of their hair color! :-)