But Hana refuses to give any reason why. She only says "It's a bad idea, please listen." There are many reasons why she doesn't give any reasons, but without any solid reason to not go, she goes. Hana doesn't know Maria is a half elf, by the way. She just believes it has a likely-hood of being true.
Yes, if you only take only her eyes into account, she does have elvish DNA. So does Ashley, and Ellen, all dark elvish DNA too. Ashley even has stronger dark elvish eyes. But eyes are not the only thing to go off of. Most people in Syl'anar actually show signs of elvish DNA, but it's almost impossible to tell a half elf with clipped ears apart from a normal human with only elf eyes. I built this world to be vague like that, because in the end, the line between elf and human doesn't matter, or shouldn't.