Since Reese Zhao came unannounced, it was impossible for Sierra not to agree to return the brooch to Adrienne. She initially thought that as long as her father was around, and if she begged their grandfather, Adrienne wouldn't be able to retrieve the brooch. Oh, how she hated Adrienne more than ever at this moment. Even when they were younger, Sierra had always hated Adrienne. She was lofty in nature and would never accept defeat, especially against Adrienne.
She didn't know that Adrienne was aware of her and Ayla's hatred towards her. Naturally, it was because her cousins also loved Alistair Han. However, Adrienne was vocal about her infatuation with him among the three of them. It also didn't help that her status as the eldest miss of the Jiang family gave her an advantage against them.