Oh geez, she looks awful. Feeding live is a self-punishing act...she seems to have gotten bit in the mouth with a blazing infection...she needs a vet a.s.a.p. IMO.
Brownish fluid sounds like old blood mixed with oozing from the wound. Poor snake! Bet you wish you could take back that moment of feeding live...this is why
many of us get all "preachy" about feeding dead prey (either f/t or fresh-killed)...injury prevention! Snakes can die from rodent injuries & vets aren't cheap.
If that was my snake, I'd find a vet now, not wait.