Tu quoque fallacy

When i'm in primary school...i use to quarrel with my younger sister..but it never our relationship. Still remember the year which i'm in 16years old and she was 14years old, that day i told mum i go for tuition class but the truth was i went for a movie with my boyfriend. At the same day, i was saw my sis in the cinema(both of us get shocked), as i know my sis told my mum that she went to her friend's house to discuss her homework. I straightaway pull her to a side and asked:" why you were here?? you suppose to be in yours friend's house discussing your homework,!! you lying to mum!!" Then my sis said:" you shouldn't be here also!! i know you had told mum that you are attending the tuition class right now but you go for movie with a guy. You can't said i lied to mum because you also did the same thing!!" At last, we decided to keep it as secret and don't let our mum know it.......:P

Implment from critical thinking:
Im using the tu quoque fallacy which is one of the fallacy in ad hominem fallacy.
~I straightaway pull her to a side and asked:" why you were here?? you suppose to be in yours friend's house discussing your homework,!! you lying to mum!!" Then my sis said:" you shouldn't be here also!! i know you had told mum that you are attending the tuition class right now but you go for movie with a guy. You can't said i lied to mum because you also did the same thing!!"