I think I have figured out the confusion with Betty Manning being married to 2 different men.
There were 2 Betty Mannings and they married their husbands 9 days apart (if the dates are correct).I think the fact that there were 2 Betty Mannings close in age and in the same area have confused many people.
1.Betty Manning b. 1730 married Thomas Stearns on Mar 14, 1751.
2.Betty Manning b. 1720 maried Isaiah Chaffee on Mar 5, 1751.
To make it more confusing, the 2 are related. Betty (b. 1720) is granddaughter of Samuel Manning & Abiel Wight (2nd wife). Line is Samuel (b. 1644) - Ephraim (b. 1686) - Betty (b. 1720).
Betty (b. 1730) is great-granddaughter of Samuel Manning & Elizabeth Stearns (1st wife).Line is Samuel (b. 1644) - John (b. 1667) - Samuel (b. 1703) - Betty (b. 1730).
I hope the above is correct and helps.I was quite confused for a while about Betty being married to 2 men at the same time.