According to Qiu Wentian's explanation, Royal Power Divinity could forcefully command things within a certain range of oneself.
Of course, all within the bounds of 'what is possible.' For instance, turning water into ice or causing the ground to rise were attainable, but turning an ordinary person into a giant of light was clearly not possible.
Otherwise, she would have used the divinity to change her own body.
At that time, on the Great Tang's Ironclad Transport Ship, she had used her divinity to calm the sea surface, allowing her to safely approach the enemy ship and cut it in half with a single strike, turning the tide of the naval battle in favor of the Great Tang.
If during concealment, one were to use the traits of this kind of divinity, it might indeed be possible to escape the attention of the Three Corpses God.