How is Gilly's relationship with Mrs. Trotter different than William Ernest's relationship with Trotter?

William is only seven, and he doesn't see Mrs. Trotter as a foster mother, but a true mother. He loves her deeply, and she loves him back.

Gilly, however, initially wants nothing more than to escape Mrs. Trotter's home. She wants to be reunited with her mother (she hasn't seen her in eight years), and she is even willing to steal money to achieve her goal. Luckily, Mrs. Trotter, is a kind woman, who does not press charges for the theft.

Over time, Gilly learns to respect and love Mrs. Trotter, but she then makes the mistake of writing a disparaging letter about her faster mother in order to garner her attention.... she is them removed from Mrs. Trotter's home and sent to live with her grandmother.