Rachael Phillips was born about 1832 in St Clair County, Alabama. She seemingly disappears after the 1850 census – her other sisters were still living at home and there doesn’t appear to be a marriage record. Further research would involve looking at nearby Rachael’s and eliminating those options.
1840 US Census
Rachael Phillips is noted in the 1840 census as a mark in the Female 5-10 years old. She is living with her parents, William and Sarah, in St Clair County, Alabama.

1850 US Census
The only known record with her name, so far, is the 1850 US Federal Census. She is living at home with William and Sarah in Blount County, Alabama, and is noted as 18 years old. She had not attended school in the past year nor married.

Beyond this record, I do not know what happened to her. Some have linked this Rachael with the Rachel Phillips that married Newton Harris Garrett, but I do not believe this is the same woman. She always notes her parents as being born in North Carolina, and none of the other children do that. It is likely she did before 1860, but I have yet to find a grave yard that she may be buried in.
Future research should focus on what happened to her!