As such, Gerl may have been the composer of the aria "Ein Weib ist das herrlichste Ding", for which Mozart wrote a set of variations for piano, K. 613 (the composer may instead have been another singer-composer in the troupe, Benedikt Schack).
The attribution of "Ein Weib ist das herrlichste Ding" to Gerl is being questioned, with Mozart composing piano variations on it, K. 613.  Another performer from the troupe, Benedikt Schack, might have been the actual composer.