Oh, it's titled "Sovay, the Female Highwayman"a

Here's the Pentangle version:

Sovay, the Female Highwayman

Sovay, Sovay all on a day
She dressed herself in man's array
With a brace of pistols all by her side
To meet her true love, to meet her true love, she did ride.

As she was riding over the plain
She met her true love and bid him stand,
"Stand and deliver, young man,' she said
"And If and you do not, and if and you do not, I'll shoot you dead!'

He delivered up his golden store
And still she craved for one thing more;
"That diamond ring, that diamond ring that I see you wear
Oh hand it over, oh hand it over, and your life I'll spare.'

"That diamond ring I wouldn't part
For it's a token from me sweetheart;
You shoot and be damned, you rogue," said he.
"And you'll be hanged, and you'll be hanged for murdering me.'

Next morning in the garden green
Young Sophie and her love were seen;
He spied his watch hanging by her clothes
Which made him blush lads, which made him blush, lads, like any rose.

"Why do you blush, you foolish thing,
I thought to have that diamond ring;
'Twas I who robbed you all on the plain
So here's your gold, so here's your gold and your watch and chain.'

"I only did it for to know
Whether you were a man or no;
"If you had given me that ring," she said,
"I'd have pulled the trigger, I'd have pulled the trigger and shot you dead.'