YOU SAID:

She sells sea shells on the sea shore, but the shells she sells aren't sea shells for sure

INTO JAPANESE

彼女は海岸で貝殻を売っていますが、彼女が売っている貝殻は確かに貝殻ではありません

BACK INTO ENGLISH

She sells shells on the beach, but the shells she sells are certainly not shells

INTO JAPANESE

彼女はビーチで貝殻を売っていますが、彼女が売っている貝殻は確かに貝殻ではありません

BACK INTO ENGLISH

She sells shells on the beach, but the shells she sells are certainly not shells