Harries, who won 78 Wales caps and scored 28 tries for her country, announced the end of her Test career after 14 years in midweek and was one of her side’s try-scorers in the play-off double-header.
The former Scarlet was one of five try-scorers for Thunder, with centre Ellie Tromans, wing Amy Williams and lock Shona Wakley and replacement hooker Amy Morgan all crossing for tries before Harries landed her drop goal in the dying moments.
Thunder looked like a different side from when the two sides met in the Celtic Challenge opener at the start of the year.
Lightning had won the first historic clash between the sides in the new expanded cross-border tournament when they ran out 20-5 victors at Rodney Parade on New Year’s Day.
The all-Welsh clash was part of a unique double-header with Irish side, the Clovers, and Edinburgh with both sides sharing the spoils in a 12-12 draw in the final play-off round to mark the end of the tournament.
Harries was given a standing ovation by the crowd when she ran out ahead of the Thunder at the home of the Scarlets, her home region. It was a fitting tribute to a player who has given so much to the game.
Both sides made early fumbles in a nervy opening before Thunder opened the scoring when centre Tromans snapped up a loose ball after a period of pressure by the home side to make it 5-0.
Wing Williams then stretched Thunder’s lead when she crossed in the corner after some suffocating defence saw the visitors spill the ball and the home side took full advantage.
The home side then stretched their lead with a third try when lock Wakley crashed over from short-range before Harries followed suit with Thunder’s fourth and bonus-point try. Fly-half Mollie Wilkinson added the conversion to make it 22-0 at half-time.
After the break, Lightning rediscovered themselves and looked like the side that had impressed earlier in the tournament.
When scrum-half Seren Singleton was yellow carded for a professional foul flanker Maise Davies crossed for a Lightning try from short-range to make it 22-5.
Normal service was resumed when replacement hooker Morgan scored Thunder’s fifth try before Harries signed off with an audacious drop goal to make the score 30-5 on the final whistle.
