Well, oftentimes particularly with love, you have to experience the act and feeling to understand it. Poetry and music is enjoyable but does not do the experience justice.
The stage one romantic love vs stage 2 committed long term love is the difference here. Until she makes it to stage two and experiences that fully and commits to reciprocating, she will continue to think "love" is just stage 1 romantic love.
What's worse, in my opinion an affair just presents the illusion of stage 1 romantic love.
Your spouse and mine are both doubly confused, first with the full and rich understanding of all love has to offer, and second with the idea that an addictive sex affair is any kind of love at all.
I believe she and most humans have he capacity, it is a matter of them having the impulse control to push themselves into a lifestyle where they can experience and understand love in its full flavour.
She's hooked on coffee and doesnt' realise that fruit juices not only exist but are also a lot healthier for you.
She CAN drink the fruit juice. Its a matter of willingness.