Hello & welcome, I am Dr. B, a licensed veterinarian & I would like to help you with your wee one today.
This is a very unfortunate situation for Zelda, since what you have described is more suspicious of her having been hit by a car then attacked by another cat. And as I am sure you can appreciate, she is limping and struggling due to pain. Therefore, she really does need a vet (especially since human pain relief drugs are toxic for cats). Therefore, since you noted financial issues, I do want to leave some information that could help you both.
First, there are 2 chain vet practices called Banfield and VCA that offer afree first consultation. This would at least offset some of the cost of having her seen and treated. You can find the vouchers for these at:
VCA veterinary hospitals(http://www.vcahospitals.com/main/offer) or
Banfield Veterinary hospitals(http://www.banfield.com/landing-pages/coupon?)
Otherwise, if you don't have a branch near you, then I would strongly advise checking the Humane Society's database @ http://www.humanesociety.org/animals/resources/tips/trouble_affording_pet.html They have a lot of branches nationwide, along with ties to other assistance organizations, that can keep down costs and subsidize careand surely will be willing to help in a situation such as this. The same goes for ASPCA (https://www.aspca.org/about-us/faq/financial-help-my-vet-bills) and they too wouldn't want her to be suffering as she is and therefore are likely to help.
Please take care,