She is voiced by Akeno Watanabe in the Japanese version of the anime and Jamie Marchi in the English version.
Liz has dark blonde hair that reaches her mid-back, dark blue eyes, and slightly sun-kissed skin. She has a smaller breast size than her little sister, which annoys her to no end, though she is much taller and slightly older. Both of the Thompson sisters wear cowgirl outfits: tight, sleeveless red turtleneck belly shirts with white ties, cowboy hats and black high-heel boots. However, unlike Patti, Liz wears long jeans and two silver bracelets on each wrist. In addition, there is a subtle difference in their hats. Patti's hat has rounded rims, whilst Liz's hat has rims that slant forward. In the anime, as the series progress, both Thompson sisters wear cropped white jackets over their outfits. Liz's soul has a pink color and has two curved triangles representing her hat.
When 'studying' for the Super-Written Exam (she mostly procrastinated through all of it), she changes into a purple business outfit with a head band brushing back her hair, two heeled shoes and a pair of reading glasses. This is referred to as her "smart-girl transformation". Her glasses have not been seen again for the rest of the series, so whether she requires reading glasses or not has as of yet not been clarified. Saying this, they are referred to as 'fashion glasses' or 'glasses for looks' in the manga. However, she is shown to be intelligent enough to pass the Exam without studying as much as the others, scoring higher than Patty, Black☆Star and even Death the Kid, who admittedly, couldn't even write his name.
In her new Spartoi uniform, Liz wears a zip-up top over a blue vest and a white sports jacket over it. She no longer wears her cowboy hat, and her jeans are replaced by a blue pleated skirt.
Out of all the characters, Liz changes the most physically when entering the Book of Eibon. Her appearance is that of a heavily-built man with closely cropped hair and piercings on each ear, wearing a white jacket and dark pants. Despite her threatening appearance, she still displays her squeamishness and cowardice, much to Patti's amusement. Also, she along with Tsubaki remain in their opposite gender form the longest, revealing that they are the most lustful out of the group. However the most lustful of them is Tsubaki, as Liz turns back to normal slightly before Tsubaki.
While Patti is very child-like, Liz is more like a teenage girl (worried about makeup, shopping, looks, etc). Despite mostly being the cool-headed and serious of the sisters, she is shown to be extremely afraid of paranormal things, convinced that any ghost she meets is out to eat her (where her paranoia severely irritates the ghosts that are trying to help her). She can also be a little cynical and shallow sometimes (but not always), and sometimes takes advantage of other people for her own gains, like when she pretends that Tsubaki's cooking is her own to impress a boy she likes. She can be flirtatious and can also be charming to men, mostly in order to deceive them (which is shown when she tricks Giriko alongside Patti).
Both Liz and Patti admire Kid's dignified soul due to the fact that they are from the streets. Unlike Patti, Liz finds the drama brought on by Kid's perfectionist attitude annoying. Also, Patti adores her and thinks that Liz knows everything.
It is shown, both in the main series and Soul Eater Not!, that before she and Patti became Kid's Weapons, they were much more cruel and selfish. In one of Liz's flashbacks, she and Patti were mugging an old man, saying that they wouldn't hurt him if he gave them his money. After Liz snatches his briefcase, she hits him over the head with Patti (in Weapon form).
She is the older and more mature of the two sisters. Kid's obsession with symmetry and how he will let it control his life sometimes gets on her nerves and she frequently reprimands Kid for this, although she won't hesitate to cheer him up when he is depressed. She also displays wit, courage and determination whenever her friends are in danger, and tries her best to protect them.