The "unfamiliar line" spoken by the girl was "I'm not after your money" (or words to that effect).
The (unspoken) fear of most men in a relationship is "she is a gold digger." These fears have been stoked for at least two centuries by (feminine) social commentary like the following:
"It is a truth universally acknowledged that any single man in possession of a good fortune must be in want of a wife."* [emphasis added].
The "Summer Wine" woman was memorable for convincing the hero that she wasn't like that.
But the fifth verse (two verses after the one you cited) tells a different story:
"When I woke up, the sun was shining in my eyes
My silver spurs were gone, my head felt twice its size
She took my silver spurs, a dollar and a dime
And left me craving for...more summer wine
Of course she was, and when he took "inventory," a dollar and a dime" were missing, as were his silver spurs. (To give you some idea of value, "in the old days," the value of an ounce of silver was a dollar (now about $15)).
*I'm not sure that the first claim of "Pride and Prejudice" is actually true. I believe, however, that it is "universally acknowledged," thanks in large part to Jane Austen.