She takes it off in [Astonishing X-Men #56][1]

[![enter image description here][2]][2]

[![enter image description here][3]][3]

As to *why*, it's because she's removed it to adjust it, and then can't be bothered to put it back on before having her lunch.


  [1]: https://marvel.fandom.com/wiki/Astonishing_X-Men_Vol_3_56
  [2]: https://i.sstatic.net/j3oWa.jpg
  [3]: https://i.sstatic.net/HMNTQ.png