I don't think just wanting to die is enough to make people's blood super appealing to monsters, unless Shiori was lying about how suicidal people smell like decaying beached whale (For all we know THAT may be the most irresistible smell for monsters). Maybe it has something to do with being the sole survivor from a family, or maybe Hinako was marked by a monster and that makes her more delicious?
It's always questions and more questions reading this.