Why did Voldemort offer to spare Lily?

[frumenta]

No: HPFGUIDX 175820

--- In HPforGrownups at yahoogroups.com, "eggplant107" <eggplant107 at ...> 
wrote:
>
> In GOF Voldemort says "Lord Voldemort rewards his helpers", Snape was
> Voldemort's most important lieutenant, if he asked him to spare
> Lilly's life the Dark Lord was willing to grant him that favor
> provided she didn't cause too much trouble. Unfortunately she did
> cause too much trouble. 
> 
> Eggplant Gellert Grindelwald
>

I don't see how she caused trouble, really. She was standing in front 
of the baby's crib, wandless and pleading. It's not like she was 
shooting curses at him and he got her by accident. She was wandless. 
He could have stupefied her, petrified her, turned her into a slug... 
a number of things and then just killed Harry without a hitch. Lily 
wasn't really trouble to him but it was in his nature to kill (he 
thought it more prudent to finish them all) and so regardless of his 
promise he did kill her.

Mim