Use of 'decline'

Hi

This is how decline is used in my part of the world. Could you please tell me if the use sounds fully natural to your native ears?

1. I offered her a lift but she declined.
2. He invited me for lunch but I declined.
3. I asked him for a little loan but he declined.
4. A- Will you come to me birthday party? B- Sorry, I must decline. I'm flying tonight.

Thanks,

Tom