There are many people who believe that the Earth is flat and even more that they believe that the moon's landings were false.
There are hundreds of conspiracy theories that make the rounds, a great thing that deserves to be analyzed.
Your friend has every right to believe in what she wants, but the worrying thing is that she seems to be reading nonsense, mainly on social networking sites like Facebook and believing everything she reads.
You seem to be sensible enough to ignore these theories, so I suggest you try to convince your friend that they are nonsense.
There is ample evidence available to refute the theory of the "flat Earth", and there is also much evidence that the landings of the Moon took place.