anger, vexation, angry, indignant
悻 centers on a strong, resentful anger: feeling vexed, indignant, or openly angry about something unjust or frustrating.
悻 combines the heart radical 忄 with 幸. The exact historical role of 幸 here is uncertain; it may have contributed sound, but the modern form does not clearly preserve a phonetic or semantic link to anger.
The heart radical 忄 beside 幸 (happiness) creates a sharp contrast: when expected happiness is denied, the heart fills with indignation and anger.
For ケイ, imagine a person named Kay who is always indignant about small injustices: Kay -> ケイ, and her angry heart 忄 flares up beside the idea of happiness 幸.