It's been rumored that Stacy Fathers character on Superman and Lois may be an old school Supergirl villan. Check out the end of episode 1x03 and you will see why the rumors are most likely right. Kara is both the only female kryptonian on Earth!
Stacy Garber plays Leslie Lar, which seems to be a take one the old Supergirl villain Lesla-Larr. Considering what she did at the end of episode 3, shrubs most likely the CWDCs version of that character.