Up against a physical Scottish side, Wales went 7-0 down and faced long periods defending their own line.
As the game wore on, Becky Dando (UWIC) began to dominate the lineout and Wales were rewarded with a try from winger Rachel Brown (Bangor).
Stacey Saunders (Tylorstown) kicked a penalty to put Wales 8-7 up before replacement winger Becca Stilwell (Carm Quins) raced clear to put Wales 15-7 ahead, Saunders converting.