That looks, to me, like the same type of sores my AmBulldog gets on his feet due to allergies and exactly what it looks like when he licks at them. If you can't afford to see the vet, you can try this and see if it helps... Do you have a set of dog clippers, or can you borrow a set? If you can, I would shave the entire foot with a #15 blade or as close as you can get to that, against the grain of the hair. I would soak the foot before shaving in warm water for a few minutes to loosen up the crust and gooey bits, and then pick/pull as much of that off as you can get off; you want it off of there to help with healing and shaving off the scabs is more uncomfortable than doing it this way. Squeeze and pat dry as much as possible, especially between the toes and pads. Use a 50/50 mix of rubbing alcohol and white vinegar on cottonballs all over where those sores are; I hate to say it, it's going to sting pretty badly, but that should clean it up and then dry it out. Keeping it dried out is crucial. I wouldn't put anything on it, no socks, etc, but keep an e-collar on her to prevent her from licking at it which keeps it moist and gooey.