Delara headcanon/history
/!\ English is not my first language so please don't judge my level /!\
So this is my own headcanon but i like to imagine that Delara is in Nya's family line (like a lot of people ik but let me explain).
So she was the sister of Maya's mother, few time before her sister annonced she was pregnant, Delara join Nadakhan on his ship and became his girlfriend (he never has infinite wishes before married Nya so he couldn't be married to Delara). Not as long before Maya birth, Soto and his pirates captured Nadakhan and killed Delara.
Her family heard about her death some days after Maya birth. They decided to never talk about her existence to the newborn and future elemental master of water (probably because of the shame of having a pirate daughter in couple with a djin). That's why Maya never knew about her aunt and couldn't tell about her aunt to her childs before leave them.
This explain why Nya is the exact portrait of Delara and why Nadakhan believed she was her dead girlfriend (that absolutely not excuse what he do to her and the ninja) .