I'm afraid let you disappointed that the words just only comes from its sound. Didn't have too much meaning, but I'll explain each of word at the below.
詩思妮 is sound like [shih sih ní]
My first time looks the name "Cecile" I'll guess that should speak like [sih sə li], its sound is very similar to "詩思妮"
But I use google to speak "Cecile" is totally different then I think. It's speak like[sə sēl]
So if really want to translate for that, I would say that is comes from the sounds of name. And select each word to let it becomes elegant.
詩 , the place of ambition, when it in heart , is an ambition, when you speak, it becomes to poetry.
思 , wise and farsighted.
妮 , young girl.