Like many of Dickinson's poems, "I measure every Grief I meet" deals with death, and rather directly, to boot. But here's the thing. All that grief in the poem? It's not necessarily caused by death. Sure, Dickinson drops the ultimate end in there, but she also emphasizes that other griefs—the really long lasting ones, can come from other tragedies, like cold and despair.
By stating that death is "but one" reason why people feel sad, the poem minimizes death's importance as a cause of grief.
When the speaker "wonders" if others have thought of suicide, she is really hinting at her own suicidal thoughts.