Nestael was born under unusual circumstances after horrible events led to her conception.  After her rebirth she grew at a supernatural rate.  However, as she aged, the aging process slowed.  Currently she appears as a young girl not quite into her teen years.  However, there is an agelessness to her eyes, and a maturity to her speech that betrays her true nature as a Maiar.

There is something of her mother's physical features in her, for those who know Hattie, but they are overshadowed by the otherworldlyness unique to the Ainur.  In addition, there is a physical perfection about her that any father would be both proud of and horrified by, any female would desire to posses, and eventually any suitors would do anything to be near.  One can only imagine what Nestael looked like when she first came to Arda, a full Maiar.