The Ospreys started brightly, with Murray accepting an interception pass in the opening minutes to outpace the cover from the halfway line. With the conversion missed, it was the turn of the Blues to put pressure on the Ospreys. Rachel Green converted a penalty for the Blues to make the score 5-3.
However, good attacking work from the home team led to a lineout on the Blues 5m line. The ball went over the jumpers to the back where the impressive youngster Delyth Davies snaffled the ball and fed Siwan Lillicrap who powered over the line.
Bethan Preece made amends for an early penalty miss to add the extras. The Ospreys survived more Blues attacks and a sin binning for a high tackle going into half time ahead.
The Blues immediately hit back on the restart whistle, taking a quick tap penalty after an infringement from the kick off. Former international Carys John managed to sneak through the defence to bring the scores to 12-10 with the successful conversion.
The Blues lineout started to function well, with catch and drives taking them closer to the Osprey line. Sterling defence kept the Blues out. Ambition got the better of the Ospreys though and a loose pass in the 22 led to Natasha Peters running over from an interception under the posts, setting up another straightforward conversion.
By now it was all defence for the Ospreys. Several attempts to breach the defence were thwarted before the ball was turned over on the Ospreys try line. The ball was shifted swiftly down the line to Murray, who beat her opposite number and rounded the full back to run under the posts for her second try.
With the game evenly balanced at 19-15, the Osprey were continually tested, before Peters added another try. Finally, one of the finds of the World Cup, Blues hooker Lowri Harries ran in from 22m line after neat work on the blindside from Wales scrum half Laura Prosser. Green slotted the conversion from the touchline.
The final 10 minutes of the game saw the Ospreys in the ascendancy but they could not find the last pass. A dropped ball was kicked clear and the match ended with a jubilant Blues delighted at their hard fought victory.
In the other game played at Ammanford, the match had to be abandoned in the second half - with the Scalets leading 10-8 - when Dragons centre Clare Flowers suffered a serious leg injury. The match will now be played at a later date.