A rinse with hydrogen peroxide is a good way to draw out any impurities in the area, and it is safe to use on the lips as long as she isn't drinking or swallowing a significant amount of it.
You can bring the swelling down and decrease discomfort by letting her have a popsicle now and then. Stay with the clear frozen liquids as opposed to the creamy ones.
You might also want to try applying a little bit of organic coconut oil to the area. Coconut oil has antibacterial properties, and is the oil that most closely matches the human body's own natural sebum, encouraging healing. It will also keep her lips moist so chapping won't be an issue. Since it's a food product, you won't have to worry about toxicity.
Poor little thing! I hope it heals quickly.