This is meant to elevate Lin Wan'er's status.
To call it an elevation isn't entirely accurate. The daughter of Yin Hu isn't of a lower status than the daughter of the Duke Mansion. Nonetheless, being alone and unsupported in the Capital City, Lin Wan'er needed someone with real backing.
Now, someone is backing her—this is truly help in her time of need.
By the time Yin Hu's old subordinates come looking for her to pledge allegiance, supporting her then would merely be an embellishment.
Consort Li is adept at seizing opportunities.
Lin Wan'er's face was filled with joy, but she didn't immediately agree and instead looked toward the elderly matron behind her.
This seemingly unconscious move deeply pleased the old lady.
The elder matron, smiling kindly, said, "Wan'er, this is your blessing, so why not quickly address her as your godmother?"
Shyly, Lin Wan'er used sign language to call out "Godmother."
Lu Luo added, "My young lady is addressing you as godmother."
