There is no problem with giving the main character a best friend, just please dont make it the "I love 1D/5sos so much please come to the concert with me" best friend. Some fanfics started that way, and usually the point of that best friend is to give the main character an image that she doesnt like the band or that she isnt so obsessed with it like her best friend. Some fanfics do give their main character that best friend, and sometimes they make it work. What I mean by that is they dont go overboard with how the best friend acts, and dont make her annoying. The best friend asks the main character to go with her to lets say a meet n greet and dont get me wrong she begs but honestly you should know when the begging has reached its limit. There were many times where Ill read a fanfic with "that best friend" and she just kept going on and on and its like enough already.
Bottom line dont have the "ILTSM" Best Friend.
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I hope you liked my first chapter :) sorry if I sounded rude, but Im just being honest. Please vote and Comment! Thank You! ~ Zoni