If an opponent's creature attacks my defense position creature and in response I destroy it with a trap or spell, do I still have to flip my creature?
If my opponent attacks my face down creature and I destroy her attacking creature with my trap, do I still have to flip my creature at all?


If you destroyed it before damage step then you don't have to flip. 

This you can do when the attack is declared. This is the first step of the attack action. If you don't prevent it here, then you will proceed to Damage Step and then Calculation, where you will then have to flip your monster.

As per my answer to your past question, there we can see an example of how a flipping may or may not take place during an attack. Again, it will flip if you let it continue to Damage Step, and then even though the attacking monsters dies your flip monster can still be destroyed by the attack if it's defense is lower.