AITA for refusing to cover for my friend’s lie about being adopted to avoid doing a family tree project?

My best friend (16F) is very dramatic. When our history teacher assigned a family tree project, she didn’t want to do it because her mom is “too embarrassing.” So she lied and said she’s adopted and doesn't know anything about her biological family.

The teacher asked me (I’m her partner on the project) to confirm, and I said no, she’s not adopted.

She got called out and now half the class thinks I’m a “rat.” AITA?