You quietly, and respectfully, move on.
It can be tempted to want to “do something” when a CEO is seemingly destroying a startup. You can take it to the board of directors. They may listen. But it’s unlikely they will do anything. You can rally the troops. But they aren’t the boss.
There’s no good play here. The CEO is the boss, until the board decides otherwise. But she’s the boss.
If you don’t think she’s the right boss, find a better place to work.
You may be right. But sometimes, also, it’s hard to see the whole story. Sometimes no matter how messed up things seem, the CEO the company has is its best current option. Oftentimes, any other alternative is worse.