RTA: sort of.
In fact, leave the fuselage out of the equation - the effect of a fuselage on the behaviour of the winglet is very small (consider, for a wing of about 50ft semi span, your winglet might be 3 or 4 ft high - that means the fuselage is some 10-15 times the "winglet span" away from the fuselage, and a good rule of thumb is that to really influence a wing (or winglet in this case) you need any obstruction to be within about one span of the wing; so ground effect is usually important within one span's dimension of the ground, etc.)
The winglet has NO parasitic drag in the aftwards aircraft direction; the forward vectoring of the resultant force takes care of that. And the force isn't negligible; it could be a significant percentage of the overall winglet effect, depending on the flow geometry and the design of the winglet.