Superman and Lois will FINALLY acknowledge those Supergirl questions before the end of season 2.

"All I'll say is that I think everybody has this question why we don't bring up Supergirl or The Flash or any other heroes...and I'll just say at the end of this season you guys will get the answer to the questions you have"

At Wonder Con yesterday they confirmed that we will finally get a Supergirl reference ( or an appearance .. they wouldn’t say which ) during the Superman and Lois S2 Finale