I always took "Do I know you?"as her really saying "I don't know you so I dnt want to talk to you". Because if she did know me she wouldn't be asking n its obvious tht she doesn't if you're sending the friend request n were never friends before. Even if she was slightly interested in accepting the friend request she wouldn't be askin questioning the friend request.
At least I never took this as a shit test just tht she wasn't interested cause if u just send out a friend request n nothing else, she msgs u with tht u didn't do anything wrong; she's just not interested. If she's not even receptive in accepting the friend request u sent out, thts it there's nothing u can do to turn tht around accept waste time trying to get into a frame battle/neg warefare/whtever u guys are doing to devalidate or 'IOD' to get her to react to n u win the frame on fb. I dnt think tht really works cause u already sent out the friend request communicating interest so u cant take tht back cause she now already knows n is IODing u .IODing her back isn't going to change her mind unfortunitely cause she already made her mind up. Thts just my opinion . I wwouldn waste my time on stuff lke tht.