I played with my girlfriend in a world for some time and suddenly she got gray bars on her diet and they don't grow if she eats since we entered the nether. Don't know what could cause that, on my character everything works fine.
Thanks in advance for those who can help or tried to.

Ok I discovered after few minutes after the post, all I had to do is the /diet resume (playerName) and it turned to normal, I don't know how, but it seems that after she entered the nether it paused her Diet.