It is swollen & looks infected to me. I personally would take her to the vet to see what they think, she might need an antibiotic.
You could try soaking the foot in epsom salt water, Here's how to do that:
Get some epsom salt, fill up a shot glass with warm water, put about 2 tablespoons of epsom salt in the water, and put her foot in it for a few minutes. Have someone hold her and you put the shot glass to her foot.
The sooner you start these soaks the better (tonight if possible). I had a chin whos toe got bit off and the epsom salt helped more than blu-kote or neosporin (thanks to Peggy for the idea). I still used neosporin after the soaks to prevent germs from getting inside the wound.
If this gets any worse or no progress is made go to the vet, especially since she is picking at it.