I'm sorry but I had to respond to a family crisis. I am back now.
I would be worried that she has a foreign body like a seed or grass awn stuck in there. Even though you are not seeing an entry site, it is still a possibility. If that is the case, then I would continue with the epsom salt soaks and either it will eventually work its way out, or it will abscess open and need to be treated with antibiotics. You can try hot packing the pad to help it work its way out. Use a wet face cloth and put it in the microwave for 30-40 seconds. It should be very warm but not too hot. wrap the paw and keep it like that for 5-10 minutes. Do this a few times per day. The lump may be an abscess already forming and she may already be at the point that antibiotics (and pain medication for the limping) may be needed.
Another possibility is that Ginger has a cyst or growth that is in the pad and you are now able to palpate it. The dog's paw has many small glands and it is not uncommon for some of them to become cystic or even cancerous. Cystic is much more common (and benign) fortunately.
I would recommend continuing with the epsom salt soaks and also do the hot packing for a day or two more, and if she is no better, then take her to be examined by your vet.
You should also try to keep her from licking at the paw, so if you have an e-collar (cone) I would recommend using it for the next few days. You can also give her an 81mg aspirin every 12 hours to help with the pain as long as she is otherwise healthy. If she vomits or has diarrhea on the aspirin, discontinue its use.
Good luck and I hope this helps.