The correct way to say "you love cookies!" is:
B. Me encantan las galletas.
This translates to "I love cookies." However, if you are specifically wanting to say it to your friend as if you’re expressing that they love cookies, you might want to say "¡Te encantan las galletas!" which would correspond to "You love cookies!"
So the correct answer in terms of addressing your friend directly should actually be:
D. Te encantan las galletas.
My apologies for any confusion!