Yes. Whenever human beings want to do something they know to be wrong, there has to be a process whereby they give themselves permission to go ahead anyway.
In an affair, that permission depends very much on the justifications someone is giving themselves for having an affair. These can vary from the banal but honest (especially if there are no relational causes for the infidelity and the person can't pretend that there are) - along the lines of "I want to do this and as long as my spouse doesn't find out, this won't hurt him", right through to the punitive "If my H had treated me properly all these years, I wouldn't be doing this, so it's not my fault really..."
If someone has fallen in love with the affair partner, the permission-process becomes all about that person i.e. "I wouldn't be doing this with anyone else, but he is too special".
With female infidelity especially, I have noticed that there is a hugely unhelpful societal discourse that for a woman to be unfaithful, she must have been unhappy in her marriage. This is an even stronger societal belief than the one held, that all infidelity must have relational causes.
However, while there remains a societal distaste for women who can have sex without love or for women having the same reasons as men for their infidelity, this myth will still prevail and sometimes the woman herself can get locked into that script, even if it is inaccurate in her particular case.
If a woman cannot with any conviction delude herself that she is unhappy in her marriage, there is a tendency to exaggerate her feelings for her affair partner and convince herself that she wouldn't be doing this if she were not in love.
Since it makes no sense whatsoever that male affair partners are inherently more loveable than female affair partners and yet unfaithful men have always been able to accept that they can have affairs without love, this suggests that gender politics still play an active part in affairs and infidelity, as they do for everything else.
Asking an an unfaithful spouse about how and why they gave themselves permission to be unfaithful is an illuminating question and one that requires enormous thought. For it to be answered truthfully and honestly, a person must try to recall their inner dialogue and this can be especially difficult if they spoke to no-one about their affair.
Even asking questions about what she told the OM might not yield the truth, because it is possible that she lied to him as well about why she was doing this, either to make him feel better about what he was doing himself, or to convince him that her feelings for him were genuine.
The most difficult delusions are the lies she might have been telling herself. You might have read some of my other posts about how for a long time before an affair starts, people in previously good marriages will often sabotage it themselves, in order to create marital discord and give themselves a justification.
In summary, the permission-giving process depends on the believed justifications for infidelity, but what were believed to be justifications at the time, are often delusions and lies to oneself.