In order to isolate her destructive divinity so that she can begin to cultivate her divinity of creation, Shiro had to achieve two things.
The first was to isolate her divinity. By doing so, she would be able to prevent it from getting stronger for the time being.
The second is to learn how to use the orb to cultivate a second divinity. She also needed to empower the second divinity until it's something that can stand on par with the Divinity of Destruction.
While the Divinity of Destruction may be tier 2 right now, it will be upgraded to tier 5 in the future.
If her memories are correct, the Divinity rankings are as follows. Tier 1 Demi God, Tier 2 God, Tier 3 Primordial, Tier 4 High Primordial, Tier 5 First Born and finally, Tier 6 which only belongs to Chaos.