Unfortunately, there doesn't seem to be a quick fix for abscesses other than complete removal of the entire capsule. Lancing and draining is a slow process. My pig, Sundae, had a jawline abscess lanced and drained last October. She was put on chloramphenicol and was sent home for me to express any extra pus and irrigate the wound. And that's what I did for months! At first I got a lot of pus out, and the amount gradually lessened over time. I used various things to irrigate... saline, peroxide, a mix of the two, and then my vet gave me a big bottle of skin antiseptic that he uses in his practice, and that worked the best. I had a syringe that I would fill so I could irrigate inside the wound. It's a long process because it really has to heal from the inside out. Sundae is now 7 months postop and still has a 'hole' in her face, although it is now a dead end with no pus and no sinus down into the deeper tissue and no longer needs special care. But it took a lot of care over several months to get it to clear, so hang in there and keep expressing.
Two things come to my mind from reading your post. Is you pig eating okay? If so, great! If not, syringe to keep her weight and strength up. Weigh her often to make sure she is maintaining. I would also ask your vet about a different antibiotic. Baytril is good for some things, but is not the best for abscesses. My vet uses chloramphenicol, and I hear good things about Zithromax, though it isn't in common use in guinea pigs where I live. There are some other members here with a lot of abscess experience... I know I got great advice going through Sundae's abscess ordeal. Lots of luck- definitely ask me anything that might help!