Hate to say it, but her appearing in a third Deadpool movie might be her best shot.
Have her show up and cause havoc. Deadpool hears about her and assumes she's a crazed fangirl or something and goes after her. A fight ensues, until the real villain shows up, and they team up to beat him. If Disney and fox are fully assimilated by this point you can even include references to the larger mcu. Gwen would also basically have the same origin as in the comics, except for movies.
Not very original, but this would probably be the best way to introduce her.