"
ni'o la snime blabi cu ze'u ze'u cpana lo nenri be lo mrovau gi'e fusra na gi'e ja'a simlu lo ka sipna"
1) "ze'u ze'u" is not recognized by genrei or jobski. If it is in fact not permissible, might I suggest "ba'e ze'u"?
2) You got tripped up here due to the default grouping of multiple logical connectives. This says that she was "not (both lying a long time in the coffin and decaying) but seemed to be sleeping" In other words, she either was not lying a long time in the coffin, or not decaying, or perhaps both. Not what you wanted. Stick a "bo" after the second gi'e to solve that.
--gejyspa