Tennyson; Lancelot and Elaine

In the end of the reading Elaine sings a song, The Song of Love and Death:

"Sweet is true love though given in vain, in vain;

And sweet is death who puts an end to pain:
I know not which is sweeter no, not I.
Love, art thou sweet? then bitter death must be:
Love, thou art bitter; sweet is death to me.
O Love, if death be sweeter let me die.
Sweet love, that seems not made to fade away,
Sweet love, that seems make us loveless clay,
I know not which is sweeter, no, not I.
I fain would follow love, if that could be;
I needs must follow death, who calls for me;
Call and I will follow, I follow! let me die."

 If we break it done line by line one can get a better feeling of her emotions after Lancelot refused her.
"Sweet is true love though given in vain, in vain -- true love is a good thing even if it's not reciprocated.
And sweet is death who puts an end to pain -- death is an escape, once you're dead you feel no pain
I know not which is sweeter no, not I. -- She is unsure what to do, suffer through life with her one sided love or to die?
Love art thou sweet? then bitter death must be:-- If true love is worth the pain then she should abhor death
Love, thou art bitter; sweet is death to me.-- But her feelings do not make her happy, she doesn't want to live with her one sided love. Death is preferred love is abhorred.
O Love, if death be sweeter let me die. -- Now she pleads with "love" to die because she prefers death to her love for Lancelot.
Sweet love, that seems not made to fade away, -- to her the love is still sweet but it will not fade away for the entirety of her life.
Sweet love, that seems to make us loveless clay, -- her she seems to be lamenting how her love is not returned, she loves someone who in her eyes appears to have admitted to being incapable of love.
O know not which is sweeter, no, not I. -- this could just be a poetical thing on Tennyson's part to keep the proper rhythm of the poem but if not  she would be indecisive about her decision.
I fain would follow love, if that could be; -- she'd rather follow Lancelot if he'd have let her.
I needs must follow death, who calls for me; -- but she can't so she must follow death, her only option (in her eyes) left. The lure of death calls to her.
Call and I will follow, I follow! let me die." -- Death calls and she decides to follow. She commits herself to dying and so declares her own death in the end of her song.
It gives a little more sense of her then Mallory did but they both agree on the same thing, Elaine decides to she can't live without Lancelot and so dies of a broken heart.