When my gf (who would become my wife of 23 years, and soon to be my ex) first said, "I love you", (about 3-4 months into the relationship) she expected me to say it after her...
I knew that, but didn't...
....long pause....
Her: "Why didn't you say you love me?"
Me: "Because I don't know if I love you yet, or not. We haven't had a fight yet."
Her:

Her: "What do you MEAN, "we haven't had a fight yet"!? What's THAT got to do with love?!"
Me: "During a fight, a person will say things that are mean and hurtful...but if you're in love, "true" love, you won't. Or, if you do (because of emotions), you'll immediately apologize and calm down."
Me:

Her:

...Well, that turned out to be our first fight. LOL!
A few days later, after she'd calmed down, she realized the truth of what I'd said.
Our divorce is not related to this, btw.