Jesus mourned for Lazarus after Lazarus died -- even though Jesus had plans regarding Lazarus. Eventually, Jesus came to the tomb, which is a cave that had a large stone covering the entry.
Jesus told Martha to take away the stone (11:39), but Martha had some questions inside. Martha told Jesus that Lazarus was dead for 4 days. It's common Jewish belief that the soul departs from a dead body after 3 days (Jewish Funerals), so it's likely that in Martha's view, it's too late for Jesus to do anything about it.
However, Jesus proclaims that believing in Him results in experiencing the glory of God (11:40). Even in times where it's hard to find hope, we can have hope because of Jesus's promise to experience the glory of God when we believe in Jesus. For Martha, Jesus would go beyond her expectations.