Shortly before the outbreak of the Clone Wars, Owen's step-mother, Shmi Skywalker Lars, was kidnapped by Tusken Raiders, an event that brought Shmi's son, Anakin Skywalker, and his soon-to-be-wife, Padmé Amidala, to the Lars homestead.
Three years later, when the galactic conflict came to a close, Beru and Owen became the guardians of their new baby nephew, Luke Skywalker, after his father turned to the dark side of the Force and became Darth Vader. Nineteen years later, Beru and Owen would be discovered by Stormtroopers who subsequently killed them, but Luke was out of harm's way to receive their demise.
Beru was well-loved and respected by all who knew her. She was highly intelligent, kind, caring, and compassionate towards others. Beru also had a playful side; she and Cliegg Lars, her then-future father-in-law, were known to sometimes engage in verbal sparring. Beru had a strong work ethic and was considered an excellent wife for Owen Lars by those around him. Although she supported the Galactic Republic, Beru was uninterested in traveling across the galaxy. Content with her life on Tatooine, she also used to play with her step-nephew, Luke Skywalker, when the latter was still a child, and when the family was low on money, Beru never complained and asked for little from her husband. In fact, her only large request was a droid that spoke Bocce to help her around the house. She loved her husband Owen dearly, as did she her step-nephew, who was like a son to her.
While her husband, Owen would accost Luke whenever he would become curious about the Jedi or show signs of his strong Force-sensitivity, Beru was far more lenient when dealing with these situations. She would admit, in vague response, that there was truth to stories her step-nephew had heard of swashbuckling warriors who once fought for peace and justice throughout the galaxy. When it came to Obi-Wan Kenobi, Beru was outwardly far more courteous to the Jedi Master than Owen - who saw completely isolating Luke from the elderly Jedi Master as the best means of protecting their step-nephew. Beru quietly disliked when Owen raved against Luke's Jedi protector, but did not stop him.
As Luke got older, Beru would often serve as the mediator between him and Owen, presiding over their disagreements, while the increasing tension of such disputes deeply saddened her. So, apart from more mystical matters, Beru was also far more accepting and supportive of Luke's dreams, such as his wish to join the Imperial Academy, than Owen was. She quietly fought for Luke's cause when speaking with her husband and was the one who suggested that Luke stay at the homestead for the last year before leaving for the Academy so Owen could raise enough money to hire someone to replace him, placating both her nephew and husband with the arrangement. Although Beru wanted Luke around as much as Owen did, and respected her husband's desire to stop Luke following in his father's footsteps (but she inwardly did not support this; as it was not Owen's place to decide for Luke, not to become a Jedi, as the latter was already old enough to make his own decisions). She also knew that Luke needed to get away and pursue his passions.
A New Hope
Nineteen years after adopting Luke, Beru and Owen bought R2-D2 and C-3PO from Jawas. Along with Owen, she met her demise from the Empire's Stormtroopers who were led to their home, and was killed before Luke could return home and save them.