A male has asked his female friend to attend a destination wedding with him. Does he pay for her?

Depends on his intentions... he really should offer to pay for the trip. Best thing is to speak to the female friend openly about this, especially if he has budgetary issues.

Why not come right out and say which you are? If doesn't make any difference here.

Okay. If your b/f has asked you to attend, then it should be "dutch treat" you pay yours, he pays his and split expenses when you get there. That is fair.