My daughter is mad I won't let her dye her hair🙄

My daughter randomly asked if she could dye her hair blue for her 16th birthday. I told her no. Personally I don't want her to dye her hair, but that's not the reason I said no. Her school has a strict dress code. She goes to a private school and they will suspend you for colored hair. She got mad at me and says it's a stupid rule. Regardless if it's stupid or not we still gave to follow it, so now she's refusing to talk to me. Ugh. I'm never gonna get through these teenage years