Welcome to the best guinea pig forum around!
A C&C cage would be the best first case of action. If you plan to get a friend for her (which I
strongly encourage you to do), then you'll need at least a 2x4. My motto: bigger is better!
I honestly think that a friend would help your guinea pig recover from the suffering she's endured in the past. You can start your search for an adoptable guinea pig at
PETFINDER.
Make sure your guinea pig is really a girl. I'm thinking she was bought from a pet store, where guinea pigs are frequently missexed. Check out
THIS page for how to sex your pig.
Before you adopt another guinea pig, please take a look at
THIS page for information about bonding, introducing, etc.
You'll [obviously] need to be extra gentle and quiet around your guinea pig until she gets used to you and her new surroundings. It'll probably be a while until she starts to calm down.
To make her feel secure, wrap her up in a blanket while holding her. This works well with the skittish guinea pigs at the GP rescue I volunteer at. Also, try to spend time with her, as often as possible. Hold her, pet her while she's in the cage, clean the cage, feed her. Do whatever you can to get her used to your presence.
Good luck, and welcome! We're always here if you have any more questions.