When Alexis did not see the enemy ships, she could only assume that they fled to their own planet. She thought that they might have run away after seeing a large number of military ships. But what she did not understand was why the leader's ship was still there. Not that she was ungrateful about that. She was really glad that the ship was abandoned along with her.
It would have been her worst nightmare if she was taken to their planet. She wouldn't have any crafts to make a return trip to Celine. And she would have most probably been killed by those vengeful Titans.
And not to mention, she had just returned to Celine yesterday, after spending around a year in old Celine. She definitely was not ready for another adventure, that also all on her own and to the enemy planet.
And there was also another thing that Alexis did not understand, "Why are we still hovering in the sky? Are those Titans going to return with an even bigger force?"