Yes, I agree she has learnt to prolonge her time outside with you by holding off going to the loo because she's taken straight back inside when she has been.

It is also common for dogs to ask to be let out purely to get attention even if they don't actually need to relieve themselves. They know that if they go to the door and ask to be let out, everyone goes rushing because they think they need the loo. If a dog can't get your attention in other ways, it can often learn that doing this is the sure way to get it.