She has shown to be motherly and protective, as well as a kind ruler over her subjects.
In "Descendants", she is initially friendly towards Mal until her granddaughter Audrey informs her of Mal being the daughter of Maleficent, causing Leah to (unfairly) unload her loathing of Maleficent for causing her to miss out on her daughter's entire childhood onto Mal (and unknowingly help Mal realize the pain of others), which spurs Mal angrily back to her mission of gaining the Fairy Godmother's wand.
Queen Leah and her husband are the monarchs of an unnamed kingdom, in medieval Europe. After many years of marriage she gives birth to a beautiful baby daughter which she and her husband name her Aurora. Her happiness is shortened when Maleficent, who was not invited, curses her daughter. Devastated, she has to see her daughter taken away by the fairies in order to protect her. Sixteen years later she is waiting the return of her daughter, but when Aurora touches the spindle, the Queen and the entire kingdom are put in a sleep by the good Fairies. When Maleficent is defeated she awakens, and finally meets her daughter, whom she embraces and cries tears of happiness when she sees her.
In the short segment, Stefan, Leah, Hubert, and Phillip all go off on a royal ceremony where Hubert is due to give a speech. Trusting their daughter, Stefan and Leah give Aurora the "keys to the kingdom" while they're away.
In the ABC fantasy drama series Once Upon a Time, she's called Briar Rose (as a reference to Sleeping Beauty). The original Sleeping Beauty, she had incurred Maleficent's wrath, and was cursed by her into an eternal sleep before King Stefan awakens her with true love's kiss. While Maleficent falls into ruin, destroyed by her failed revenge, King Stefan and Briar Rose marry and have a daughter named Aurora. Years later, when their daughter is set to wed Prince Phillip, King Stefan seeks to get rid of Maleficent permanently to keep Aurora safe from her. Instead, Maleficent regains her lost ability to morph into a dragon and gains the upper-hand over the king, but the latter managed to survive. Later, Maleficent gains retribution against Briar Rose by cursing Aurora into an eternal sleep.
Queen Leah appeared in the film under the name of Leila and was portrayed by Hannah New. She is the daughter of the ruthless King Henry. She remains loyal to her father who performs her duties as princess by becoming Stefan's wife and later bearing his child. She would soon witness Maleficent, her husband's former friend whom he betrayed would place a curse on her daughter Aurora.
During the course of the film she becomes gravelly ill and eventually dies. Stefan shows no grief over her death as he has become paranoid and obsessed with hunting Maleficent down.
Queen Leah appeared in the Disney Channel Original Movie played by Judith Maxie. By that time she is a grandmother to Audrey. She is shown to be non-sympathetic to the the villains especially Mal, because her mother caused Leah to miss out on her own daughter's entire childhood. After the incident at the coronation, she appears to have accepted Mal and the others; she observes as Audrey thanks Mal for stopping her mom.