You have received good advice from the others so I won't go over treatment options for the lice and mites.
If you have photos of your hen you would like to share, we will be happy to take a closer look.
You mentioned she is pale and possibly anemic, that very well could be due to the infestation. In addition to her regular poultry feed give her about 1tablespoon of chopped liver or quality canned dog food daily. When you have the resources, poultry vitamins like Rooster Booster Poultry Cell or Rooster Booster Vitamins/Electrolytes with probiotics would be good to give as well.
I do understand about money being tight, but also consider getting a fecal float or de-worming too. You don't mention your location, but a lot of times
State Labs offer services such as fecal floats/testing at minimal cost compared to Vets.