First he has diabetes and his diet regiment includes no drinking alcohol. So if he drank so much that he passed out his glucose level would have skyrocketed and would not have come back unless he had been hospitalized and in ICU for a number of days.
Second he is not a woman who would forget if something happened after getting drunk. In any case memory is intact.
Third, Arnav said previously that he broke up before the graduation day.
Fourth and most importantly she said Arnav drank so much that he passed out. Arnav has diabetes. So if he passed out how come she did not take him to the hospital and he would have passed out much before then he got drunk.
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