When someone is contradicting someone else?

basically, if you contradict someone you are being irresponsible by either already knowing the answer or instantly saying something that may not be true,

for example: your girlfriend didn't answer your call and when she does you ask her why she didn't, she will give you a reason and then you instantly say "you were seeing your other half"

it isn't nice to contradict people but its a habit we all have, i myself contradict people alot but i find it fun.