Violet was born during the summer before Emily's senior year of high school, which is partially documented in "Twisted," "Ruthless," and "Stunning." Emily originally planned to give her up to a family, the Bakers, but she was attracted to the offer of wealthy socialite Gayle Riggs. However, she was not sure if Gayle was a good fit and instead left her baby on the Bakers' doorstep who then took Violet in.
Several months later, Emily drives by the home only to find out that it has been put up for sale. Eventually, she finds the Bakers and her daughter living in another town in Pennsylvania. At this point Violet is seven months old and from what Emily could see, Violet looked like a normal, happy baby and the Bakers promise to tell Violet about her when she's older.
In Vicious, Emily decided she wants to be in Violet's life. The Bakers are planning to take Violet to Disneyland when she's two, and they invite Emily to go with them.