Does this data isolate for women who are heavily religious and unlikely to realize there may be better partners out their for them to live a happy life with?

Religious beliefs pressure people heavily to stick with their first partner, even if that partner is abusive. If you ask me the long term success of a marriage is better measured in how happy both partners truly are within it and not simply the length. I would hazard a guess that a similar chart of overall happiness within a marriage based on previous partner count would have a standard Bell curve, showing that a few partners leads to significantly increased overall marital satisfaction.

But in that case, as in this one, there's way too many variables to consider this chart with any significance. Though it likely appeals to whatever narrative you already believe considering your statement.