I just checked the WoT timeline. According to this timeline, Aran'gar left the Rebels on day 746, while Graendal has her PoV in TGS (where she still believes that Aran'gar stays with the Rebels & that Aran'gar doesn't know her lair) on day 753.

It makes no sense that Aran'gar didn't find a new own lair in the meantime, but strolled with Delana for at least 7 days through the Westlands as homeless persons till Graendal showed enough mercy to allow them to move into her palace.