Originally she was standing near the fountain next to a cart on Caldeum Bazaar. After Patch 1.0.4, Squirt had heard that many people bought potions at the Hidden Camp, so she moved up there. As of patch 1.0.6, Squirt the Peddler has also been found just NE of the waypoint in the hidden camp, and is the best vendor to sell all the trash acquired in Act II to.
There is an amulet in game named after her (or, perhaps, once hers).
Squirt's threats to hurt anyone who tries to steal from her have become a sort of a joke among players.