oh! it seems she HAS to land the crit  hit first in order for the increase ATK to activate...  so its a 50% 50% chance for this ability to work.  But it's not what the description say, it say it place I ATK on champion and has the opportunity to land a second hit if the first is critical. how it's describe it say it place I ATK and the extra hit is only possible if the first is crit. So its either bugged or the description is bad write, either way there is a mistake here.

it's official. i investigate further i found the Increase attack buff  sometimes triggers and sometimes don't , very random, doesn't matter if the first hit is critical or not. clearly it's bugged.