It could be simplified "She is not the thinnest nor the fattest"
'neither is she the fattest' would be the best English
I think I'd argue for "nor" over "neither"
both better than "also"
This sentence is awkward, "...SHE IS also not the fattest" is the more natural translation
Wouldn't "She is not the thinnest, not the fattest either." be OK?
Sounds good to me
"She is not the thinnest, also not the fattest." isn't correct in English. You need something like "She is not the thinnest and also not the fattest."
(s)he is neither the thinnest, nor the fattest
She us neither the thhinnest nor the fattest
The pronunciation is not good