Not to come across in an acrimonious way (all the time researching the LAMBS over the years has made them seem like a second family), but solid historical facts outweigh speculation. Elizabeth HEMPSTEAD (1672-1733) was NEVER married to Isaac LAMB (ca 1664-1723). There's not a single shred of HISTORICAL EVIDENCE to support a HEMPSTEAD/LAMB union. The ONLY way to connect Elizabeth HEMPSTEAD to Isaac LAMB is to purposefully IGNORE the historical and genealogical record.
The HEMPSTEAD-LAMB connection was wrongly contrived by LAMB researchers over the past 125 years seeking a surname for Elizabeth E. Lamb, wife of Isaac LAMB of Groton. However, Elizabeth E. Lamb was still living 4 years (Nov 1737) AFTER the death of Elizabeth Hempstead Plumbe on 19 Sept 1733 (Groton Town Records, Groton Deeds Book 4, page 61; dated 21 Nov 1737).
There is no credibility to this claim of a HEMPSTEAD/LAMB connection; if LAMB tree builders spend a minimal time searching the readily available historical record (Let me name 3: New London Vital Records, Connecticut Town Records (Barbour), and THE DIARY OF JOSHUA HEMPSTEAD, published by the New London County Historical Society), they would quickly clarify the truths about the marriage of Elizabeth HEMPSTEAD to John PLUMBE on 13 Feb 1689, and eliminate the confusion of this alleged marriage to Isaac.