I have found the parents of Olive, thanks to Ancestry posting the newly released Mass. records...
Her father is Ephraim SEGAR (1749-1806), born & died in Spencer, Worcester MA. His parents were Oliver SEGAR Sr. (1721-1803) & Lydia CLARKE (1730-1791), both of Spencer.
Olive's mother is Olive BARTON (1763-1821), of Oxford, Worcester MA & the daughter of Caleb BARTON (1704-1763) & Susannah MARCH (1718-1770) of Sutton, Worcester MA.
Olive SEGAR (1790-1855) was m to George LEONARD Jr. (1776-1833)at the age of 15, in Franklin Co VT, very soon after her father's death in MA. Her 1st cousin Roderick SEGAR (1781-1850) married Thankful LEONARD, the sister of Olive's husband George. Roderick (abt 1781-after 1850) was son of Henry SEGAR (1760-) & Rebekah HAYWARD (1764-) and also was born in Spencer. I have not yet figured out whether anyone else sent with Olive & Roderick to VT.