Who would really leave the luxury of the Enterprise to work on a tug boat like Voyager? Wasn't it bad enough they kept bringing back a nobody character like Boothby in uncreative ways?
Q, Riker, Boothby, Barclay, LaForge & Troi, wasn't there enough TNG cast on Voy. without adding Guinan?
Purhaps a personal quest to find more of her people?
Granted not exspecting to be sucked into the Delta quadrant.
Although you say that she wouldn't expect the Voyager to get pulled into the DQ, Voyagers initial mission was simply to head out to the Badlands and locate the Maquis under Commander Chakotay and bring them, and Tuvok, back to Starfleet. Beyond that would assumedly have been general Starship exploration.
Guinan wouldn't also be needed as initially Voyager didn't have a Bar, only a wall with Replicator units on it.