Fantasy story - original enough?

i love the twilight series, but i'mnow trying to write my own fantasy story and it seems as if i can't do it without copywriting Twilight or Harry Potter or Tolkien or whatever. i'm having a girlnamed Rina who leaves in a houseboat by the ocean in california, and one day when she ventures out too far on the coast she meets an Armiri [underwater creature] named Felix. Armiri's are sort of like mermaids, but they have webbed hands and guys don't have tails; they have webbed toes. i want some romance in it, but i don't think i can make Rina and Felix fall in love without copying Twilight; and i'm worried that the name Armiri is too similar to the Arturi in Twilight and the Inferi from Harry Potter. help?! do you think it's copywrite, and if so, ideas?? [as detailed as possible, please?]. o yeah and i just thought of something else whats the difference between ( ) and [ ] ?