It's natural that when a human is starving they will obsess over food. What happens with some anorexic people is that they fear that if they even mention food their resolve to not eat will collapse spectacularly and they will binge on food and not be able to stop, ever. So they cut food out of their life as much as they can. She is probably thinking about food but she dare not look at food, talk about food or cooking because for her it's a slippery slope. It's as bad as eating in her mind.

She dreams about food because she can't control her starving body and brain while asleep. That could be why she has this issue with sleeping. She doesn't much like sleep and she doesn't need it, probably because it's full of temptation that she must avoid at all costs. I think she thinks about food all the time but makes a constant effort to push those thoughts away. Thats why food talk is banned in chat on twitch. If she just wasn't interested in food, chat about it would still be allowed because it wouldn't be the huge threat it really is too her.