Can Kai'sa's Daughter of the Void ability be used to pay for Deflect costs of single target spells and reflexive triggers?

Ruling: Kai'sa's Daughter of the Void can be used to pay for Deflect costs of single target spells, but cannot be used to pay for Deflect costs of reflexive triggers.

Nuances:

• Kai'sa's ability specifies a spell, while reflexive triggers are abilities, not spells
• Even though reflexive triggers identify the spell as being the source, the triggers themselves are not spells
• You can use abilities like Windwall on the full spell but not on the reflexive triggers