Lal is a highly advanced android offspring constructed initially by Data, with heavy influence by Deanna when she learned about it. Lal was initially presented to us as Robotic Lal, who ultimately chose to resemble Deanna. After this idea being rejected by Data, they agreed on a modified hairstyle. After questioning why Data didn't want to make any cosmetic changes to Lal, she finally and sarcastically congratulated Data when Lal was completed.
Lal was technically months old by this point, and only a few weeks of sentience. Despite being over 5 feet in height, 60 trillion simultaneous calculations per second, and the strength of ten Klingons, nothing like that changes the fact that she is still a very young child with fragile delicate emotions. Nobody saw that coming, as Data himself is supposed to be emotionally benign, and Lal is supposed to be patterned after him. Nevertheless, Lal had exceeded Data's abilities by taking far less issue when using English Language Contractions.
Lal had been quick to learn from the very beginning, and continued to do so by matching tactile responses correctly. She however, was unable to differentiate a real flower from a painted one, which is very common among young children. Later, they decided to enroll Lal in class. Initially, they wanted her to attend high school or some type of technical academy, but did not seem up to the challenge. She was placed with younger children with similar personality. Data and Beverly agreed with the teacher's report that while some children were amused by her youthful, free spirited personality, the rest of the children mistook her as another school teacher, and were very intimidated by her. Everybody compromised by taking her out of traditional class entirely and send her off to employment with Guinan.
However, as Picard was worried about it earlier, Lal's success in both construction, activation, and gainful activities got the attention of both Star Fleet and The Romulan Star Empire. Vice Admiral Anthony Haftel arrived to warn them about The Romulans as well as the unacceptable disaster that occurred with Doctor Richard Daystrom's M5 Multitronic Tactical Unit. Since Daystrom's envy of his peers cost the lives of several thousand citizens of The United Federation Of Planets, Admiral Haftel urged them to a much more organized social and academic and workforce environment that proved to be much safer from a Romulan attack.
In addition to mentioning how unacceptable it is for Lal to remain so isolated, to which he noticed that the only compromise that is available aboard ship is to be a so called Cocktail Waitress, it also seems that some type of unresolved issue occurred between Admiral Haftel and his own children. It seems that Haftel wants to raise Lal as a substitute for the loss of his children. He even sounded more resentful towards children even more than Picard himself, who started to come to the defense of Data and Lal. Admiral invoked an order that he claims is empowered to utilize, with Picard appealing.
Nobody had realized until it is too late that Lal is still a young child in many ways, and that an abrupt move literally traumatizes any child. She sought guidance from Deanna, who both agreed that Lal became emotionally unstable, and located the nearest science lab to wait for Data. After notifying Picard and Data, Haftel accompanied them to the science lab. No longer able to quarrel with each other, Data and Haftel gladly worked together in attempt to prevent any more system failures.
Haftel expressed surprise and also regret about his attitude towards highly advanced, dangerous, and vulnerable technology, as well as his attitude towards children, and any combination of both. He listed Lal as Killed In Action in order to distract The Romulans while Data and Lal have their final moments alone. Data copied Lal's memory engrams and other uncorrupted files from her before deactivating her for the final time. Not much is known about what happened to her body. It is most likely it eventually ended up together with all the other known Soong Type Androids. Others such as an incarnation of Doctor Julianna Tainer had mixed reactions toward Lal and her demise, and informed Data to slow down and do much more research before attempting to work on any androids. During this time, Data had learned how to effectively dream, and years later, became addicted to his emotion chip. By the 25th century, it is implied that Lal was indeed resurrected, though not by Data himself.
