I doubt that she ever even thought of that. Back in the '30's women were expected to play "roles", and there were no Gloria Steinhams or others to awaken them to other possibilities.
Vivian felt trapped in a loveless marriage, but for her the only escape was another man, even if he was a worthless lout. So, until her tragic end, she still played a "role"--Loftus' mistress.
I do not think Vivian's marriage was loveless nor do I think she felt it was. Yes she married the first man who asked her but love can grow in a marriage. She was confused about what she wanted out of life. Her husband did love her and when they talked about it he admitted he was at a lost - he gave her what she wanted. If there was something else he would do what he could to please her. (Hence a trip.) She did not make it clear what she wanted/needed; she only knew it was NOT to be near him. (Hence the trip without him.)
In my opinion what they had was a marriage without passion but if they had gone to marriage counseling or whatever was able at the time they would probably have found ways to make the marriage better. Sounds like this husband would be willing. It is not uncommon for people to have "disillusions” about marriage but once they look at it clearly, maturely without lust in their eyes maybe more marriages can be saved.
On the other hand, some people seem to be born with a hole in their soul (I mean that in the vernacular, not in any religious sense) that defies definition or explanation. Pretty hard to repair something you can't understand or quantify.
The more we learn about brain disorders, the more likely it seems it could be attributable more to neurons and chemical uptake rates than life experience.
Vivian could be suffering from a lack of love, or of fulfillment. She could also have a mental health disorder no one could even have fathomed in her day.
Nothing to see here, move along.