Fanny is the second of ten children. Her parents were not very well off and having ten children was hard for them. This forced her mother to reconcile with her two sisters, Lady Bertram and Mrs. Norris, after they had been estranged for nearly eleven years in order to ask for help. Her uncle, Sir Thomas Bertram, a wealthy baronet, offered career advice for Fanny's brothers, and Lady Bertram sent monetary aid. The real help was conceived by her Aunt Norris, who suggested that they invite Fanny to Mansfield so that she could receive an education and relieve her parents of some burdens. Her mother was surprised because she thought the sons would be more sought after, but acquiesced and was pleased. Sir Thomas did leave the caveat that they would send Fanny home if she proved too vulgar to train.
She arrived at Mansfield when she was 10 years old. She was awed by the splendor of the estate and her relatives. She began a friendship with her 16 year old cousin Edmund after the boy had found her crying of homesickness. He offered to help her write and post a letter to her elder brother William, whom she dearly missed. She was not considered bright by her female cousins, who talked about her ignorance. She soon rose above that and proved to be teachable, pleasing her uncle. She shared a governess with her female cousins, a Miss Lee.
Uncle Norris died when Fanny was 15 years of age, leaving Aunt Norris a widow. She was apprehensive and saddened when her aunt Bertram told her that she was sending her to live as a companion for Aunt Norris, whom she didn't really like. It turned out that Mrs. Norris did not want a companion nor did she want her young niece to stay with her, and instead concerned herself with the Bertram girls. Her uncle, Sir Thomas, left for Antigua with his eldest son. Fanny became Lady Bertram's companion, especially when her cousins were out and enjoying the small society of their village. She had no share in the festivities and instead spent each function reading, listening, and talking with Aunt Bertram. She lived vicariously through her cousin Edmund, who told her about the functions.
She became disheartened when her grey pony died, leaving her without a horse. Her aunts neglected to get her a new mount, instead saying that the Miss Bertrams could lend her one of their horses if they were not using them. As they never did sacrifice their pleasure for their cousin, Fanny was stranded. Her only real champion in this case was Edmund, who said she definitely would need a horse.
Upon the dual arrivals of Mary Crawford and her brother Henry, Fanny was in a semi-awkward position. She was quiet and rarely attended social functions, which confused Mary. Fanny thought Miss Crawford was very beautiful, but continued to think Henry was rather plain. Mary deduced that since Fanny never attended balls and hardly ever spoke in public, that the other young woman was indeed "not out".
Fanny was dismayed when Edmund went riding with Mary Crawford and other young people instead of with her. He restarted their daily rides when he learned the mistreatment she got from her aunts while he was away. Due to Edmund's kindness, she was also able to go on an outing to Sotherton Court. She was slightly disappointed in Sotherton and voiced her opinion in a low voice to Edmund.
- Main article: Edmund Bertram
Fanny always had a close relationship with her first cousin. He was kind to her when she first arrived, and stayed friends with her during the whole of her time at Mansfield.
- Main article: Henry Crawford
Henry Crawford was in love with Fanny and proposed to her, but she rejected him. She ended up marrying her cousin Edmund.
Uncle and aunts
- Main article: Sir Thomas Bertram
Sir Thomas had been wary of bringing Fanny to live with his young children at the beginning, but the girl soon settled in. He proceeded to help Fanny and her siblings throughout the rest of her young life. She is grateful to him, as one can see when she discusses Mary Crawford's callous words about the uncle who took her in.
- Main article: Mrs. Norris
Fanny's relationship with Mrs. Norris, one of her maternal aunts, was rocky. The lady could be thanked for bringing her to Mansfield, but was generally callous and dismissive of Fanny and tended to favor her wealthier female Bertram cousins. Mrs. Norris viewed Fanny more as a servant than her niece and even had her do manual labor when it was hot out. Mrs. Norris's dismissive attitudes toward Fanny annoyed and shocked Edmund Bertram.
- Main article: Lady Bertram
The lady was kind to Fanny when she first arrived, earning the girl's liking. Later, Fanny became the companion to her aunt after Sir Thomas went abroad to Antigua to look over his estates there. Both Lady Bertram and Mrs. Norris could be described as dismissive towards Fanny, but the former's is more innocent than the latter's. Lady Bertram does not actively try to exclude or degrade Fanny as her sister does, and she genuinely enjoys the girl's company as her companion.
- Main article: Mary Crawford
Like her female cousins, Fanny was awestruck of Miss Crawford's beauty and thought her a very genial young woman. She did think Miss Crawford was being ungrateful towards her uncle, who took her in.