Elizabeth Olsen did an interview with French Premier and, amidst the usual fluffy stuff (this is the darkest Marvel movie, she says, which is a standard talking point when superhero movie actors want to express that the film is good/serious), she revealed that not only is Daniel Bruhl playing the bad guy in the film, maybe her Scarlet Witch character is too.
"She's someone who's more powerful than she's able to control and she ends up going insane because of it. And she's like a wildcard. You never know [if] she's a hero or a villain and that's a very fun part."
I'm not quite sure what to make of that quote. Is Wanda going crazy in Civil War? Rumors have pointed to her inability to control her powers creating a disaster that kickstarts the civil war itself, but is that what she means? Or is this a reference to her comic research? After all, Wanda Maximoff was revealed to be very deeply disturbed at one point, to the level that she unconsciously used her powers to create children for herself and husband The Vision (this is a storyline I'm not wild about and one that has colored the character for decades since).
If she does go crazy that could explain why she's in the D23 footage as being on Cap's team but absent from the concept art that Jeremy Renner posted - perhaps she gets sidelined from the fracas by her own issues.