I disagree. She doesn't have to marry into another dynasty to give back to her dynasty. Finding tutelage under a powerful master and becoming a powerful cultivator herself can also benefit her dynasty.
She was not an innocent girl. She came from the palace and knew the dangers of the world. Compared to the scheming and infighting in the palace, she was more willing to enter the immortal path and experience all the sufferings of immortal cultivation. She wanted to live for herself, not be called a tool for marriage and marry a man she'd never even met.