Lena mentioned the DEO when she was talking to Winn. When did she find out about it?
So I’m going to be honest, I spent too much time fangirling over the 35 seconds of screentime my adorable genius brotp had to even notice at first but yeah… this was a thing!
To me, other than Lena just finding out on her own somehow there are two more obvious ideas of how she knows about the DEO.
First idea: Upon his arrival, Winn explains that he is with the DEO and had been sent to assist Lena in building the device. When Lena said that, he didn’t look surprised so either this or the next idea would make sense.
Second idea: Lillian told her. I think this is the more likely of the two because consider this: They had to get a hold of Superman and Supergirl. Lena did not contact them herself. When leaving Catco it was actually Clark that said: “You’re never gonna guess who wants to see us.” Clark knows Kara and Lena are friends so if it were clear Lena was asking, it wouldn’t have been a surprise to him and Kara wouldn’t have looked shock when looking at the phone.
And during their exchange on Lena’s balcony Kara says:
They were clearly addressing Lillian in both situations as neither of them have harsh or antagonistic views of Lena. Lillian would not have a way to get in direct contact with Superman, so chances are, she contacted the DEO, Superman was notified that Lillian Luthor wished to meet with him and Supergirl. We have to recall that she did just show up at the bar last week as if she knew everything that was going on.
Lillian knows Kara is Supergirl most likely because of either Hank or Jeremiah. It could be reasonably concluded that she knows about the DEO for the same exact reason. Know your enemy, right?
Back at the DEO, Alex asks what Lillian wanted, so everyone there knew that Lillian reached out before Supergirl and Superman explain the back up plan. Not just Lena.
Reasons behind them being contacted? It was probably Lena that insisted they get in contact with the Supers, because why would Lillian seek permission/approval as opposed to just proceeding? She needed Lena and that could have been one of Lena’s stipulations. She did not feel comfortable proceeding without letting them know what she could do.