I will say that your understanding of the last scene is right on the money and I am also not even judging by the future episodes but everything up to 6x03 "After Life."
I took that last scene of her having someone in Spike to be able to open up to because she didn't need to protect his feelings whereas her friends were sort of already guilt tripping her and they were sort of already so depressed so she didn't want to bring her friends down. Deep inside Buffy is in pain and after the initial shock of being brought back, she went into protected mode to protect her friends feelings.
When you look at episodes 6x01 - 6x03, Buffy corpse has arise from the dead and the first thing she has to do is fight herself out of her own grave and she is literally buried alive. Season 5 was emotionally draining to and by the end when she jumped into that portal she was finally done with life. She was complete. So again, when she's back the first thing she sees is her grave, demons and fires... so she is back at the hell that she escaped from.
I always think of this when they kept saying why they couldn't bring Joyce back because you NEVER know what can go wrong by doing that. Although we saw the demon gang attack the friends, would Buffybot had been better prepared if Willow main focus wasn't on the spell to bring Buffy back? We will never know. I always think that one thing impacts another so if the friends let's say, accepted Buffy's death then probably everything that happened with the demon gang is different.
I view Buffy last speech of admitting she was in heaven but not wanting to tell her friends the truth because they would feel awful for taking away her happiness.