But honestly, it was weird even before that.
The 29-year-old showed up to the shindig with her funny friend Judd Apatow.
When he introduced Lena to the 69-year-old, Diane made it pretty clear that she hadn't been keeping up with the times when she asked Judd:
"Is this your wife?"
We all know the Trainwreck director is married to actress Leslie Mann, and by "we all" we mean everyone except Diane Keaton, apparently.
Judd cleared up the confusion and explained that Lena was just a friend. Most people would think that after this there would be a couple awkward apologies and then the conversation would become normal.
As we've established by now, Diane Keaton is clearly not most people.
Lena remembered that the actress immediately jumped right in with questions about her sexual orientation, saying: