If it was removed from her iCloud account, then someone must know her AppleID password, since that’s required to remove a device or sign it out of iCloud. She should change her password immediately.
And if they were were able to do that, then can simply set it up apwith a new AppleID. Your friend would receive no notice because it is no different than if she’d signed it out of icloud ud herself. When your AppleID is compromised, all security of a missing device is lost.