Their bass player mostly plays very simplified versions of the bass lines for the songs. In the band’s case it works as she keeps a steady groove going, and the performance really highlights the four-part vocals anyway. Their crowd dances the entire show and I don’t think anyone notices the incorrect bass lines.
I don't see a dilemma here. You've told us what she does fits with the band and the crowd loves the music. Play the songs the way she plays them.