If it is mostly swollen and not something you are thinking "stitches" about... then the best thing is just to give her a popsicle. Seriously.
Any time a kid of mine (or friend of my kid) has gotten a bang on the mouth (no teeth damage/issues---just the busted lip)... I give them a popsicle immediately. They love it/makes them happy. It takes their mind off their boo-boo. AND it is like applying an ice-pack to the swelling. Win, win, win.
And usually, it is a fairly good indicator of exactly how bad (or not) the wound is. If they stop crying for the popsicle,..... welll....... it can't be THAT bad, right? But if they are still crying or complaining that it hurts a minute into the popsicle...I'd give it a 2nd look and consider more aggressive care.