Was divorce a realistic option for her at that time, legally or socially? What would have been the consequences for her livelihood, her social status and the well-being of her children?
No, she likely would not have been able to get a divorce. While eighteenth-century gentlemen could get a divorce from an unfaithful wife, a wife with an unfaithful husband also needed to prove that he'd been extremely abusive to her.
I have a few past answers on this: