I see the title "Coup de Coeur" translated usually to Chinese as "so despairingly sad" (肝腸痛斷), but Google Translate gave the meaning of "loving something". What really does it mean?
A "coup de cœur" is a common french expression that describes an "instantaneous falling in love". The important notion here is "instantaneous" (as said in the other answer, the word "coup" means a "hit").
We use "coup de cœur" with the verb "avoir", as in "avoir un coup de cœur pour...".
You can have a "coup de cœur" for a wide range of notions, like objects, activities, songs, animals, places, etc.
Note : a "coup de cœur" is less intense than a "coup de foudre", which is much more specific to falling in love with another person.
In short, it means "to fall for (someone or something)", i.e. to fall in love.
But there are, I think, secondary suggestions as well. Coup is a very polysemous word that literally means "strike, hit", but in its many figurative expressions is more like "event" or "motion". For instance, a coup d'œil is a glance: a momentary "stroke" of the eye, a motion.
Hence, a coup de cœur is most basically a "heart event", an event or motion in which the heart plays a part. That might suggest more possibilities than just falling in love. But I'll rely on a native speaker to come along and confirm that suspicion.