Ok I found them in the 1850 census in Waterbury Vermont. They are living in the household of Thomas and Laura Smith.
It says that Eunice was born in Massachusetts abt 1788 or 1789, she is listed as being 61. Abigail is also living with her sister Laura's family. Laura and Thomas have 6 children in the house, Orrin G., Hershell, Emily, Thomas, William and Eunice.
There are a couple Orrin Fisk(e)'s in Vermont, Mass and New Hampshire around this time line, so I wonder if that is one of her family names or his.
The names Hershel, Thomas, and Eunice are clearly all family names so it seems that it is at least a possibility that Orrin is too.