Mollie was probably born in Pittsylvania Co., Va. She was living at the time of the 1840 census, and also signed a deed of land to her son Thomas in Jan 1839. But Frederick was a widower in the 1850 census (not widowed within the year.)

Profile of Frederick Quesenberry and his family on p. 137 of John P. Alderman's "Carroll 1765-1815 The Settlements." It cites, among other sources, Floyd Co. Will Book #C, p.196, records of the New Hope Primitive Baptist church, and the 1850 Floyd Co. Census, household #887. The Baptist Church records say Frederick died in 1853; but his will was dated 24 Jan 1854 and probated 23 Nov 1854. Alderman also cites Montgomery Co. marriage bond, issued 20 Dec 1793, for "Frederick Quesenberry & Molly Phillips, daughter of Tobias Phillips, surety Moses Quesenberry, consent Tobias and Peggey Phillips, intended marriage date 23 Dec 1793".

Montgomery Co. marriage records include Frederick Quisenbury & Mary Phillips by Robert Jones, in a list of 7 returns that the minister filed on 4 Mar 1794. He does not list the dates the marriages were performed. The IGI indexes this marriage as 4 May 1794, in batch 8507906, sheet 62, as 20 Dec 1793 in batch 7432310, sheet 71, and as 4 Mar 1794 in batch 7506508, sheet 60. Batch 8507906, submitted by Stella M. Scanland, is a large set of marriages taken directly from GS Films #7748 and #7749, both entitled "Montgomery County, Virginia Marriages". I do not know who the sources for the other two batches are.

1850 census of Carroll Co., Virginia, district 15, enumerated 4 Sep, lists on p. 441 as family #887:
Frederick Quesenberry, 78, born Va. (Next door to Isaac Bonds age 75. There are no other Quesenberry’s on this page.)