When Acacia was first spotted in Pack Of Secrecy's territory, she was treated as any other intruder, and wasn't welcome. Acacia told Mya and Reed, the ones who found her, she was only passing through. Acacia had a tough time with her former pack, with her mate betraying her for another female, and the two then chased her out. Acacia while heartbroken, was relieved to be free of leadership, as she was not the leading kind. Mya had strange feelings from Acacia from the start, and she had a feeling she shouldn't let Acacia go.
Going against her original instincts of act aggressive, she decided to let Acacia stay for awhile. Acacia was incredibly thankful, as she was tired and hungry after several hours of travelling. That wasn't the only surprise as Acacia had 3 pups with her. Seeing how Mya was struggling, and how the pups were scared, Mya let them stay and she didn't regret.
Acacia found her real talent with herbs, something Pack Of Secrecy was greatly lacking. In a short time Acacia became a talented herbalist, and was able to heal Pack Of Secrecy's members. Acacia's pup's also were stronger and healthier in the pack, so Acacia did not want to leave.
Mya also didn't want Acacia to leave, so she was welcomed to the pack.