I found some problems with ''Jillian's Rose'' and some slicers couldn't handle it. I used MeshMixer to make it solid, make all walls at least 1.0 mm and remeshed it all because it had a high poly count after those MM tools.
I also found a file I fixed some time ago with other software, it only has thicker walls but is also solid and without defects (Rose_PetalThickerWalls.stl). Try to print them as you prefer, I think slicers shouldn't have trouble with these files.
The original is here where also the leaves are that go with the flower: http://www.thingiverse.com/thing:26417