If you'll excuse the thread-necro, I think I've worked out why Shana says it that way. There is some detail to the explanation...
1) The Japanese word for "spoon" - or at least the one typically used - actually *is* "supuun"; it is a loanword, explained by the fact that Japanese cuisine does not traditionally use spoons, even for soup (which was drunk straight from the bowl, like tea). Modern Japanese uses a lot of loanwords, both from English and from other languages.
Because it is a loanword, it is written using katakana, as スプーン (su-pu-longvowel-n). This is actually the closest way to represent the English word using Japanese syllables (of which there are ~50, versus the ~2000 in English). The first 'u' is almost silent, which is their workaround for the frequent need to put two consonants together in foreign words. The double 'u' is the normal way of lengthening a vowel sound in Japanese. So it is pronounced like "s'puu-n", effectively as a three-syllable word (for a fairly loose definition of 'syllable'), even though it is written using four characters (and the original English word is only one).
2) The idiosyncratic way Shana says it is largely explained by the *context* in which she says it. The main point is: she's very annoyed. Observe:http://youtu.be/-OK8EusRmG0?t=1m50s
(near the end of Episode 1-03)
In the larger context of the preceding episodes, it becomes clear that she *often* gets annoyed at Yuuji (the boy in that scene). She doesn't sympathise with his position - which to him is a matter of life and death, so he's very persistent about it.