I agree with Wolfwood in that the player has the option of simply spending a Fate to ignore the compel -- this would represent excercising his willpower to supress his hunger.
As to going alone with the compel, I think that WCVs seem to have several levels of feeding. Thomas shows that very light feeding can be done subtly enough that casual observers wouldn't suspect. On the other end of the spectrum is deep feeding, which results in death -- how obvious is this? Well, in the case of a Raith, its going to be obvious that something was going on, but it might just look like porn-grade sex, with one participant suffering what could easily look like a heart attack. The Raith can't conceal that he was interacting with the subject, but can disguise the nature of what he was doing. This sounds like Deception vs. Lore, possibly with Alertness modifying (Alertness reduced by Lore, but Lore should be involved to have some inkling that it might have been more than sex; without Lore the onlooker might see the situation as odd somehow but not understand how). In between those two extremes would be, for example, feeding off the emotions in a Rave, which would be handled similarly (attempting deception to make it look like dirty dancing).
I suspect that the other WCV flavors should be handled similarly. In the example given, the character could rush forward, and try to make it appear as though they were comforting the victim -- holding them, stroking their hair, whispering gently, etc -- and all the while the victim would be panicking more and more "until his/her heart gave out", at which point the character feigns distress, etc. Or perhaps they might not feed so deeply (this might require a Discipline roll, see the 'feeding frenzy' rules for Emotional Vampire), leaving the child alive but with years of nightmares ahead of them. In either case, it would be obvious that the character is doing something, but could conceal the exact nature unless the onlooker was very perceptive and/or very clued in.
Note specifically, though, that Emotional Vampire requires touch to feed.