When you say someone on another site did a check - did they actually check parish records or simply use their subscription to search a genealogy website.
I'm absolutely certain that "they" checked the Hunts Marriage Index, a fiche set produced by Hunts FHS, which has transcribed all marriages in Hunts up to 1837, indexed by surname (which is not online). What "they" couldn't check was if the name was so far removed from Levis that it didn't show in their search which covered all marriages starting Lev or Lew
Rachel Levis married Robert Wright at Sawtry All Saints in 1827 (Hunts Marriage Index) following the death of John Levis in Sawtry in 1825 (NBI). Both were of Sawtry St Andrew. She appears to have been buried age 65 on 15 Apr 1850 at Sawtry St Andrew (NBI).
Robert Wright age 68 was living in Sawtry with the family of Thomas Levis in 1851, described as father in law (= step father) (1851 census image)
On the other site "someone" suggested that as Sawtry is only a couple of miles from the county boundary with Northants, which is even more difficult to research online than Hunts, you should try a look up request for the marriage on the Northants Marriage Index
BB