That Her full beauty is perceptible only to Her Lord is not said in so many blunt words. It is nicely couched in a subtle poetic extravaganza which comes in the next two lines of the same shloka. (shloka #12):
Yad-AlokautsukyAd-amara-lalanA yAnti manasA
tapobhir-dushhprApAm-api girisha-sAyujya-padavIm //12 //
yat : (of) which (beauty) (This goes with .Your beauty. in the first half).
amara-lalanAH : the divine damsels
Aloka-autsukyAt : because of their curiosity to have a complete look
yAnti : reach
manasA : mentally
girisha-sAyujya-padavIm : the unity status with Lord Shiva
dushhprApAm : that is inaccessible
tapobhir-api : even by great penances.