yet is used when you say i havent met you yet meaning you havent even seen he person before but when you meet someone you could say i havent met you before for example>>your friend askes you have you met (name) and if you havent but know you will be meeting them soon say i havent met them yet?? hope you understand what i mean

yet indicate that it hasn't happened up to the present time, although it probably will happen but when u don't say ''yet'' it might happen or might not

If you add "yet" it means you think you will meet the person in the future. It is like 还没。。。呢 in Mandarin. I haven't met you = 我没认识过你 I haven't met you yet = 我还没认识你呢