<headcannon>Love, for changelings, is a very different thing from typical food for ponies. Love is essential to keep them alive and well-fed. But by some genetic effect (or defect, depending on the sources), the consumption of love not only releases Leptin, which decreases appetite and increases metabolism, as well as make a changeling euphoric; but produces a mix of alchohol and a substance much like opium. The alcohol is combusted to fuel the changeling magic and sustain them, and it is suspected that the opium like substance was originally a reward system for the changeling body.</headcannon>

I just needed a reason for a changeling to be put in a drunk-like state from a very generous consumption of love. Anyway, Plan B, to feed the changeling queen so much so much love that she’s incapacitated, would have only been carried out if Shining left his stupor too late.