Thanks for the pictures since they definitely help but I'm sorry that I was off my computer when you sent them.
I can understand why you might think this would be secondary to trauma when she was playing with the other dog, and while I couldn't entirely rule it out, this possibility seems less likely to me since the swelling has been present for two weeks. I would have expected it to have resolved or diminished by now if that were the problem.
Of course, I can't know for sure but this looks like there may be an abscess or infection present underneath the skin.
I'd want to rule out an infection at the root of a tooth before anything else although a foreign body reaction is possible as well.
If this is an infection, then Psyche may need to be sedated and the area lanced and flushed since I'm not certain if systemic antibiotics would be entirely effective although it's possible that they might resolve the problem alone if you're reluctant to sedate her (for whatever reason).
I generally try to recommend over the counter treatment options for owners to consider at home but unless you have access to antibiotics, there really aren't any medications which would be terribly effective or likely to help:( But, if you do have access to such drugs as Amoxicillin or Cephalexin or Clindamycin or Baytril, please let me know and I can provide dosage amounts if I know how much she weighs.
I suspect you might be concerned about cancer which can develop in the mouth but this doesn't look at all like the cancers I've seen in the past. So, I hope this helps to reassure you at least about this possibility.
If the swelling had only been present for a few days, then it's possible that it might have diminished on its own; however, since it's been there for two weeks not, it seems less likely that this is going to happen. At this point, a vet visit might be prudent.