Princess Cadence is concerned about her marriage. She knew that Shining Armor and Luna were good friends with each other, due to how accepting he was of her when she had come back from the moon. When Celestia and Luna come to visit their grandniece Flurry Heart in the Crystal Empire, Cadence sees something between Luna and Shining using her powers as the princess of love. Scared that her marriage may be in jeopardy, she ponders and worries about how Shining and Luna really see each other.
Art credit to Nancyksu