Why did she raise her siblings?

Why did she raise her siblings?

• In the 1880 census, my great, great grandmother Emma lived with her mother & her 3 siblings-Annie, Leslie & Matilda.
• In the 1900 census, she is married to my great, great grandfather-Yost.  The record stated they had 6 kids & all 6 were living.  At the time, she had birthed 4 children-Andy, Daisy, Harrison (my great grandfather) & Arthlow.  Matilda is recorded as a step daughter. That would make 5.

Who was the 6th child? 

• I've been told that Emma gave birth to a daughter that looked white.  When the slave owner saw her, he sent the little girl to live with his sister in England.    ???
• As stated in a previous post, Leslie didn't die until 1908.  I'm not sure what happened to Annie after 1880.  

What happened to her parents?

• One of the biggest brick walls that I have is who is Emma Gatton's father?  He isn't mentioned on her death certificate. (Most likely Matilda did not know or she wasn't sure.)  

• Why is it that I can't find any other record for Nancy after 1880? ( If she died before 1900, why can't I find a death certificate?)

I could use all the help I can get with this one.