Visible crew/equipment: After Colossus and Negasonic Teenage Warhead leave the manor, the scene cuts back to the bridge where several gunmen are shown exiting cars and begin approaching Deadpool. In one of the shots during this, a gunman is shown exiting the passenger side of a car, with the camera placed behind him. In the shot, the reflection of a camera, cameraman and boom mic are visible in the wing mirror. (00:10:15)
Continuity mistake: In the bridge fight scene where Colossus and Negasonic Teenage Warhead appear, Deadpool tries to escape Colossus' handcuffs by severing his hand. The hand that he cuts off is his left, but when he jumps off the bridge the severed arm is on his right side.
Trivia: Wade Wilson is on the "Dead Pool", seen briefly at the back of the bar, but so are various celebrities, such as Bill Cosby, Kanye West, and Charlie Sheen. Perhaps most notable are Ryan Reynolds and TJ Miller, stars of the movie.
Answer: Yes that would be how she most likely was able to tell.