Strict parents

Isabelle
Well I only live with my mom and my brother. Keep in mind that I am a senior in highschool. So my mom believes that on school nights my curfew should be the same as the time she goes to bed, 9 o'clock... Her reasoning being that I need a good nights sleep, but she doesn't realize I don't go to bed at 9... Well lately I have been trying to push it and she has been letting me stay out until 9:30, but last night I was literally 4 minutes late.. Got home at 9:34.. And she was really mad and just said "it's going to be 9 from now on out". And it was like, I was 5 minutes late cut me some slack! And then tonight, my brother and I went to the gym together, and so I figured that she would let me stay out later since I was with him, and I got home at like 9:37, and I walk in to tell her I'm home and she just says (super pissed) "I'm just not even gonna say anything". 
I feel like she is being super unreasonable about mad about nothing. I respect her rules, I just hate how she will get mad at me about being 5 minutes late. Don't know how to communicate that.