What if its both and the gith artifact holds her real memory/powers
It doesn't.
Take a look to know what is the artifact:
the artifact is a prison for a Githyanki General.
Which datamining thread confirms that the artefact is a prison for a githyanki general? (Gith herself?) I know there was a lot of speculation about it being the infernal puzzle box containing the contract between Tiamat and Gith.
