It might pose a problem. Make sure she has enough grit and crushed oyster shell in case she feels the need for more.
Don't laugh but some time ago someones chicken on this forum swallowed string also. Anyway it started to make its way out and some string was hanging from the you know what. Well this brave chicken owner would catch the chicken and snip the part of the string that was hanging out. Of course she didn't want to pull it. Well after a few days all of the string came out and everyone was happy. You might have to do the same thing. I would keep her under close observation. If it starts to cause problems (like being stuck in the crop and causing an impacted crop) you can perform surgery and remove it.
Hopefully that doesn't happen and the string will reappear soon.