The episode "The Body" gave off a very different mood compared to other Buffy episodes. By different I mean that the episode had a more realistic (real-life-ish) approach than the others. I am not saying that other Buffy episodes have failed to include some of the realistic problems that a person might face; the show had episodes about relationships, mother-daughter tensions, etc. However, the episode "The Body" is different that it focused more on depicting Buffy as a person and a girl rather than the chosen one, the vampire slayer.
Every Buffy episode highlights Buffy's journey as a vampire slayer, drawing attention to fight scenes with some hardcore music playing in the background as Buffy kicks some vampire ass. Buffy always has to deal with some supernatural problems and entities, and her ways of dealing with them are pretty casual (almost seems emotionless). Because this has been a trend in "Buffy the Vampire Slayer," Buffy was portrayed more as the warrior than a real life girl--fighting vampires and other evil creatures night after night, heartlessly stabbing them until they turn into dusts. The things happening around her were as unreal as they could get, too: from a giant insect in a form of a beautiful woman (in one of the season 1 episodes) to a demon who turned Sunnydale into a giant musical stage.
The episode "The Body" shed a very different light on Buffy. It focused on describing Buffy as a girl, a human being dealing with a very personal problem like any others: her mother's death. Unlike other episodes, there were barely any background music or sound effects, which made this episode seem more real. The scene where Buffy just helplessly collapses and vomits after getting confirmed by paramedics that her mom is dead shows that she is as vulnerable as any other people facing a death of her loved one. The episode also emphasizes that there was nothing Buffy could've done to save her mom and that the cause of her death wasn't anything of supernatural (i.e. vampires), helping viewers see Buffy as something other than the slayer.
Although, towards the end of the episode, there's this scene where a corpse rises as a vampire and attacks Dawn (and Buffy slaying the vampire, as usual), the scene has very little importance. Unlike other episodes, where Buffy has her "prelude" speeches before the actual slaying and fighting, she quietly stabs him and sits on the floor, exhausted and pale. Then the focus moves from exhausted pale Buffy to Dawn as she approaches and looks at Joyce's corpse. What is emphasized here is the sisters at loss of words, facing their mother's death. Although there are no sound effects at this moment, viewers know that Buffy and Dawn are filled with so many different emotions--sadness, regret, etc.
Even though "The Body" wasn't as entertaining as other episodes (like "Once More with Feeling"), it did a good job allowing viewers (or at least me) see Buffy as someone other/ more than a vampire slayer.