Odin and Frigga had thought me killed as an infant in war against the Angels, and in anger he had their realm sundered from Yggdrasil. In truth I barely lived and was raised there with none but my mother my adopted mother knowing that I was Asgardian. The Avengers created a ripple in reality through their too-frequent travels through time that carried me across the breach. At that time Odin was being held somewhere and Loki took the opportunity to use the Angelic armies to break him free of his prison. It was he who recognised me.
It may be also that the Asgards we hail from differ slightly. Gamora is not the woman I am friends familiar with.