However it did take them until a minute before the break to cross the Scarlets try-line when scrum-half Natalie Watkins crossed the whitewash.
Hooker Amy Lawrence increased the Ospreys lead with a try shortly after the interval before the Scarlets halted the slide with a try by Naomi Thomas. The experienced campaigner took a quick tap and with the Ospreys defence in disarray, she took full advantage to score.
However winger Charlie Murray struck back with a try and with Rachel Rees's conversion, the visitors were ahead 5-20.
Chloe Mastaglio crossed for the Ospreys' fourth try, with Rachel Ress converting but the Scarlets had the last word when Caryl James raced over, with Thomas adding the extras.
Ospreys coach Ben Rose said he was proud of the effort his side put in and was also impressed with the number of girls who turned up prior to the game who received coaching.
"Before the game we had about 50 girls from local teams receiving coaching from WRU Development Officers. Teams participated from Haverfordwest, Carmarthen Quins and Neath Athletic, and many stayed behind to watch the regional fixture which was pleasing," said Rose.
The Ospreys next game is on 27th November at Maesteg against the Dragons where there will also be a girls event before this game. To enter the girls event teams or individuals, contact Ben rose at firstname.lastname@example.org
In the other regional encounter, the Dragons came away with a hard fought 22-17 victory over the Blues.