This morning you’re going to see a lot of click bait sites claiming that Psylocke is in Deadpool 2 based on the new trailer, when that is completely false.
The identity of the new purple/pink haired mutant in the trailer is Yukio (played by Shiori Kutsuna). And Yukio is Negasonic Teenage Warheard’s girlfriend from the Xavier mansion.
Yukio is in the movie a lot, pretty much whenever you see Negasonic, and they do have a big action scene late in the movie where the two go with Colossus after a famous X-Men villain.
She annoys Deadpool because every time she sees him she says “Hi Wade!” in a cute voice. She and Negasonic also kick off the post-credit scenes by fixing something together. So, she’s in the movie quite a bit, is Negasonic’s girlfriend, and is absolutely not Psylocke.