YOU SAID:

She sells sea shells by the seashore but the seashells that she sells arent seashore shells

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海岸の貝殻ではありません

BACK INTO ENGLISH

She sells seashells on the coast, but the shells she sells are not coastal shells

INTO JAPANESE

彼女は海岸で貝殻を販売していますが、彼女が販売する貝殻は沿岸の貝殻ではありません

BACK INTO ENGLISH

She sells seashells on the coast, but the shells she sells are not coastal shells