Warning: SPOILERS for Star Trek: Picard Season 2, Episode 9 - "Hide & Seek"
Jean-Luc Picard's (Patrick Stewart) secret memory of his mother, Yvette (Madeline Wise), in Star Trek: Picard effectively retcons her appearance in Star Trek: The Next Generation season 1. With the help of Tallinn (Orla Brady), Jean-Luc faced his buried memories of Yvette and his father, Maurice Picard (James Callis), in Star Trek: Picard season 2, episode 7, but the Romulan Watcher also knew that the full story hadn't been told. At last, Picard admitted the truth he'd tried to forget all his life: Yvette, who was mentally ill, hung herself when Jean-Luc was a boy, and he blamed himself for it.
The untold secrets of Jean-Luc's parents and childhood are at the heart of Star Trek: Picard season 2. Indeed, Q (John de Lancie) claims he changed the timeline into the dark Confederation future as part of his plot to force Picard to confront the question of why he chose to be alone and avoided a lasting romantic relationship his entire life. Jean-Luc's childhood growing up at Chateau Picard with Yvette and Maurice hold the key to why the great Starfleet hero chose to remain alone. Picard remembered his mother as an "inspiration," in large part because this is what she asked of him, and he blamed his father for her death, casting Maurice as a cold and abusive man. However, the truth is more complicated as it turns out Maurice didn't know how to help his sick wife, who refused treatment. What Jean-Luc recalled as abuse was Maurice literally locking Yvette up to protect her from himself. Still, Yvette escaped her confinement thanks to her youngest son's help and she committed suicide one fateful night.
Since Yvette Picard killed herself when Jean-Luc was a boy, it completely retcons Picard's mother's lone canonical appearance in Star Trek: The Next Generation. In the TNG season 1 episode "Where No One Has Gone Before," Captain Picard meets an illusion of his mother, who is depicted as an elderly French lady played by Herta Ware, before this vision is broken by Commander Will Riker (Jonathan Frakes) interrupting the Picards. But Star Trek: Picard now establishes that Yvette never made it to old age and she hung herself when Jean-Luc was still a young boy. Picard rationalizes the retcon to Tallinn in Star Trek: Picard by saying that he used to imagine his mother as an older lady who offered him "tea and a chat." This is meant to explain Yvette's appearance in TNG to Star Trek: Picard but does it make sense?
Jean-Luc stating in Star Trek: Picard that he imagined his mother as an elderly woman in TNG has holes, and the biggest is that the young Yvette Picard obviously speaks with a British accent, just like her son and father, Maurice, as played by James Callis. So if Jean-Luc imagines his mother as an old woman in TNG, why would she be French and speak with a French accent? It's illogical and doesn't quite line up with Star Trek: Picard's total reconception of Yvette as a vivacious woman who suffered from a severe mental illness and died in the prime of her life. Maurice also appeared as an old man played by Clive Church in TNG, but that's easier to reconcile since he did live longer plus it was an illusion conjured by Q.
Obviously, Yvette Picard's appearance as an old woman was in one of the earliest TNG episodes and it happened before the bulk of Jean-Luc Picard's backstory was devised and canonically presented. Star Trek: Picard season 2 set out to definitively answer the key questions about Jean-Luc to finally give a full picture of what makes the Starfleet Admiral tick. Star Trek: Picard wanted to revamp Picard's family history but it also had to acknowledge Yvette in TNG season 1, and they did it with an explanation that amounts to a handwave. It's ultimately up to audiences to determine for themselves whether Star Trek: Picard's retcon of Yvette's death and Jean-Luc's past works, but Yvette's suicide is now canon that overrides her appearance in TNG season 1.
Star Trek: Picard Season 2 streams Thursdays on Paramount+.