Who is Abby to Nikki on the young and the restless?

Since Nikki isn't her mother but Ashley (her husband's mistress later wife) what relation is Abby to Nikki ?
Answers

Sandra S.

Nikki is her current Step Mother making Abby her Step Daughter. Abby has had many Step Mother's over the years. As follows: Abby Newman's Stepmothers: Nikki Newman (2002–08, 2013–) Sabrina Costelana (2008) Diane Jenkins (2011) Sharon Newman (2012)

Kathy

Abby is Nikki's step-daughter.

WinterRose

Stepdaughter

audrey

Step daughter. She is Victor's daughter with Ashley Abbot.

Seth

step daughter

♥♥♥𝓨𝓸𝓾 𝓖𝓸 𝓖𝓲𝓻𝓵 ♥♥♥

She is the step-daughter Ashley stole Victor Newman sperms and so therefore Abby was born.

Sheri2271

Step daughter