Because of her minor role in the film, Jewel’s personality remains a mystery. However, it can be noted that she shares similar thoughts with her husband, mainly because they share the same brain, and the hints suggested by Dr. Finkelstein throughout the film.
Jewel shares a common appearance to her husband, Dr. Finkelstein. She shares his same facial structure, and glasses and gloves. She also appears to have yellow hair, and is only seen wearing winter clothes.
During the film, Dr. Finkelstein attempts to create another creation, one that would replace Sally. In the process, he uses half of his brain and designs her to have the same facial structure as him.
During the sculpting of her face, and as Sally sneaks off, Dr. Finkelstein removes half of his brain and places it inside of the unawakened Jewel, in which he tells the head that they will indeed have conversations worth having, before the lid of her head shuts against his lips.
While creating the reindeer, Dr. Finkelstein examines the head of Jewel, fully sculpted to look like an exact skeletal replica of his own head. He then briefly cleans it.
When Christmas is saved, Halloween Town receives snowfall, and Jewel is finished and constructed. She takes Dr. Finkelstein out for a stroll by pushing his wheelchair around. Just like her husband, Jewel wears similar glasses and gloves, but also wears a fur coat and hat, and has, what appears to be yellow hair.
Despite being created by Dr. Finkelstein at the end of the film, Jewel has been noticeably absent from all further media of the franchise. Interestingly, in the video game The Nightmare Before Christmas: Oogie's Revenge, which serves as a sequel to the original film, Sally is back to living with Dr. Finkelstein and Finkelstein himself has his brain complete once more, instead of just having the half of it, as he gave the other half to Jewel.
Coincidentally, Jewel shares similar appearance to an iconic Disney villain, Cruella De Vil.
Although Jewel is Dr. Finkelstein’s wife, her last name was confirmed to be Finkelstein in Disney Crossy Road.