Ok ok, new backstory for Avery: Avery and her 'batch' of sisters were originally built and trained by Sterling with the intention of being exported to a Francophone country, hence the accent, but an administrative error leads to her instead being sent to the American market, where her new owners and young Anon like her 'defective' funny accent and behaviour and decide to keep her. The little bit of established lore she already has, like tomboyification, hair and freckles, grooming underage Anon and dating him etc, carries on as normal.
Although multi-lingual like all Nandroids, Avery is versed in and has preference for French and Belgian dialects, cuisine and figures of speech, though 11+ years of living in America has noticably influenced her in all those categories.
This opens up new avenues of Avery lore and content, actually makes her somewhat unique as a Nandroid, and can also explain personality wise why she's more laid back and 'loose' than her refined, uptight Anglosphere peers

Of course, this is all pointless because true Avery is dead (2020-2022 RIP) and everyone has moved on.