Full back Jasmine Joyce enjoyed herself by scoring four tries for the victors while No 8 Alisha Butchers set a captain’s example, crossing for a brace.
Winger Ffion Lewis and tight head prop Danielle Jenkins ensured the Scarlets remained on top by scoring tries as well. Rachael Norris chipped in with two conversions.
For the Ospreys, scrum half Keira Bevan and second row Alicia Demery touched down while Wales senior squad member Hannah Jones kicked a conversion.
