Apparently she's drinking just enough wine that her parents are noticing something weird but not enough that they actually suspect any wrongdoing. Of course this depends on how much they drink, but I would say that if her consumption was even 1/4 of their consumption they would notice something off. So assuming they drink 2 glasses a day each (it's a generous estimate, not a lot of people drink 2 glasses every day) then she would be drinking 1 glass per day, on average, which wouldn't be enough to damage her unless they were aggregated into drinking sessions once every week where she could consume 7 glasses of wine at once. I don't know if you've ever tried to drink 7 glasses of wine in one night, but even to a trained tongue that's a challenge. So let's split it and say 3.5 glasses twice a week, which would be good enough to get a good buzz going but not usually enough to be considered 'drunk' even to a small 14 year old girl. If she kept this habit up until she turned 18, her brain development would deviate from normal but due to brain plasticity there probably wouldn't be too much of a notable effect. I agree that this generous scenario would be detrimental to her health, but consuming 1/4 of her parents total liquor supply for the next 4 years would be a rather unattainable goal.
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