Nulli se dicit mulier mea nubere malle
My woman says that she prefers to be married to no one
quam mihi, non si se Iuppiter ipse petat.
than to me, not even if Jupiter himself would seek her.
dicit: sed mulier cupido quod dicit amanti,
She says that: But what a woman says to a desirous lover,
in vento et rapida scribere oportet aqua.
she should write in the wind and rushing water.
He's astute enough to know that lovers hyperbolize in the throes of passion. But even in this realization he implies that her pillow talk is sweet to him.
So what was it exactly that Lesbia said? We can confidently dismantle the Indirect Statement construction and reassemble the likely Direct Statement antecedent:
"Mallem me nubere nulli quam tibi! Ni Iuppiter ipse me petat!"
"I would prefer to be married to no one than to you! Not even if Jupiter himself should seek me!"
But here's the thing. They all surely know their Mythology even better than us, right?
What woman who knows her Mythology seriously wants Jupiter to court her? It never turns out well for the woman. First of all, he's not available to be married. He has a wife, Juno, and she's the one who always makes Jupiter's lovers suffer cruelly in the end.
Think of the nymph Io, turned into a cow by Juno.
And then there's Semele. Juno tricks her into asking her lover Jupiter to show his godhead to her, knowing it would burn her alive.
So Lesbia tells Catullus that she would rather marry him than Jupiter. In the context of Mythology this is akin to saying "I'd rather marry you than marry Saddam Hussein!"
Starry-eyed Catullus couldn't read between the lines.