There is a 12 Jan 1841 marriage of Rebecca Matthews and
John Lilley in Parke Co., Indiana. That's the same place where
her brother, Alfred, and sister Dicey Ann Matthews also married.
LDS AF records of her father William's family
(which did not include Alfred in the family)
show it is this Rebecca who married John Lilley (or Lilly)
and provide the middle name of Reeves.
Also, traditions of descendents of her half-sister Eliza Jane remembered
some relationship with the Lilly family.