Variery reports that Marvel planted fake cameos to protect to the real ones. Ryan Reynolds confirms that Taylor Swift is definitely not in the film.
“I can neither confirm nor deny any cameos in this film but I will say, in terms of characters that may or may not appear, it was always important to us that nothing in this movie feels like a gimmick,” [executive producer Wendy] Jacobson added. “Anyone showing up has a crucial story purpose or a beginning, middle and end as a character arc. It was definitely a collaborative process of seeing who fit in and who didn’t.”...One potential cameo that continues to draw buzz on social media involved Taylor Swift, who some fans theorize will show up as either Lady Deadpool or the mutant Dazzler (a role she was allegedly circling in the “X-Men: Apocalypse” days). The “Deadpool & Wolverine” team have frequently shut down the rumor, and Reynolds recently told E! News: “I will say once and for all that the cameo thing with Taylor, because she’s our friend — that is not in this film.”
From. The way I read it.... Taylor Swift doesn't have a CAMEO, but COULD have an actual role.