She's not a Mayflower descendant
Bethia Hopkins was not the daughter of Stephen Hopkins of the Mayflower.
There were two Bethia Hopkins in Hartford at about the same time. The older of the two was the one who married William Kelsey and settled in Hartford.
I am not aware of anyone who has found the parents of the Bethia Hopkins who married William Kelsey, we really do not know who Kelsey's Bethia's parents were.
There was a John Hopkins in Hartford at the same time as Kelsey's Bethia, but Bethia married back in England, so there is no reason to necessarily connect John and Bethia. However, the Hartford John Hopkins named his own daughter Bethia, but that Bethia is NOT the same person as the Bethia who married William Kelsey. Thus is is possible that John Hopkins and Kelsey's Bethia Hopkins might have been siblings (thus the two Bethias were aunt and niece)
found on ancestry.com