The Baby Pearls, who also lost to England in pool play, were the top-performing Pacific side in Botswana after reaching the knockout rounds for the first time.
Samoa finished 11th of the 20 teams, beating the Cook Islands 64-27 in their final playoff match.
The Samoans were outclassed by eventual champions New Zealand in their opening game, but went on to win four of seven matches.
Samoa head coach Lee Edwards said her players got better as the tournament went on.
“Obviously we had a couple of close losses (by two goals against both Scotland and Botswana), which set them back from their goal of making the top eight but I’m really proud of how they finished in the final game against the Cook Islands,” she said.
“Definitely what we’d expected – none of the girls had had any of the international experience, aside from the qualifying series in September, so it was just good seeing them step up with the new intensity levels and what’s expected at this level.
“…a few of them put their hands up that they’ve definitely got a look in with the open team so I just hope that they take this experience and work hard and just (keep) getting better.”
The Cook Islands only managed one win from their seven matches but were plagued by illness throughout their three-week stay in Gaborone, with players struck down by two separate viruses.
Head coach John Glassie had targeted a top ten finish before the tournament but said they were never able to play a match at full strength.
“I’m so proud of the girls the way they fought, even though they were sick,” he said.
“We had girls on the drip visiting the doctor in the morning and then rocking up for the game in the afternoon.
The fact that they could still keep fighting and keep going to the very last minute of the game that’s just a testament of their toughness and what they wanted to do for the Cook Islands.
“Yes we finished 12th – it’s not where we wanted to finish – but under the circumstances I think that it’s probably a very good result for us.”
Meanwhile, New Zealand defended the Under 21 title, beating Australia 60-57 in the final.