Continuity mistake: Between Wade stabbing Ajax to the bridge barrier and him talking to Colossus, the sun changes every shot.
Continuity mistake: When Deadpool comes back to the duplex after cutting off his own hand, he grabs a red towel off a Chevy Citation parked outside. When he enters and flops onto the floor, the towel is yellow.
Answer: We don't see what happens to Angel Dust after Colossus carries her (and Negasonic Teenage Warhead) away from the collapsing Helicarrier. Both women were unconscious and we can only assume that Colossus put Angel Dust down somewhere before returning to Deadpool for the end scenes. Her fate beyond that - perhaps escape, incarceration or even recruitment - is unknown.