The left one. It's the Giraffe's neck that's long. Not their torso.

Edit: See Derpleton from Centaurworld.

Centaurs don’t have horse necks so neither is right. It would be the body of a giraffe with a human torso starting where the neck would start

Neither. The neck is the long part, and do horse-based centaurs have horse necks?

Giraffe centaurs would be underwhelming.

I posit a different answer

Neither, a centaur has a human torso starting at the base of the neck, the left one has a long neck so clearly not a human torso. The left one has a long torso, so that doesn't fit either.

Solution: it'd be exactly like a regular centaur but with a different skin pattern

What if he wore pants?

the left one would look sick with some shades

Why not scale up the size of the human so it fits with both solutions?

I say the left but double the length of the arms.

Hands would be a lot less evolutionarily useful if they couldn't reach your mouth.

Giraffes are Artiodactyla like cattle so they would be closer in minotaur style than the Perissodactyla centaur style. Two hoofed legs, human upper body, long neck and giraffe head.

Speaking of Perissodactyla, this guy essentially is a fantasy creature. He's the centaur she told you not to worry about.

Left is more natural. Evolution wouldn't waste time lifting that much mass making the creature top heavy unless it had an absurdly good reason to.

Like it or not, this is peak male performance

The right one. A centaur is a horse with a human torso replacing the horse’s neck & head. So it’s one of those humans with the long torso, you know the type.

Now do giraffe fauns. At least giraffe centaurs have those counterbalancing rear legs, giraffe fauns would need to be half as wide as they are tall to have abs strong enough to keep themselves upright. And with those tiny spindly legs they have, even if they do leg day religiously and bulk them up they'll still be teetering about on two little hooves.

bonus question: where's the nipples?