Background: Frances Burney (13 June 1752 - 6 January 1840), also known as Fanny Burney and after her marriage as Madame d'Arblay, was an English satirical novelist, diarist and playwright. She was born in Lynn Regis, now King's Lynn, England, on 13 June 1752, to the musician and music historian Dr Charles Burney (1726-1814) and his first wife, Esther Sleepe Burney (1725-1762). The third of her mother's six children, she was self-educated and began writing what she called her "scribblings" at the age of ten. In 1793, aged 41, she married a French exile, General Alexandre D'Arblay.
Context: Frances was the third child in a family of six. Her elder siblings were Esther (Hetty) (1749-1832) and James (1750-1821), the younger Susanna Elizabeth (1755-1800), Charles (1757-1817) and Charlotte Ann (1761-1838). Of her brothers, James became an admiral and sailed with Captain James Cook on his second and third voyages. The younger Charles Burney became a well-known classical scholar and the namesake of The Burney Collection of Newspapers. Her younger sister, Susanna, married in 1781 Molesworth Phillips, an officer in the Royal Marines who had sailed in Captain Cook's last expedition; she left a journal that is a principal eye-witness account of the Gordon Riots. Her younger half-sister, Sarah Harriet Burney (1772-1844), also became a novelist, publishing seven works of fiction of her own. Esther Sleepe Burney also bore two other boys, both named Charles, who died in infancy in 1752 and 1754.  Frances Burney began composing small letters and stories almost as soon as she learned the alphabet. She also could be found often with her brothers and sisters creating plays; both writing and acting them. The Burney family had many close friends, one of whom was a writer called Samuel Crisp, nicknamed "Daddy Crisp". He was almost like a second father to Frances, and was a strong influence on her early years of writing. Burney scholar Margaret Anne Doody has investigated conflicts within the Burney family that affected Burney's writing and her personal life. Doody alleged that one strain was an incestuous relationship between her brother James and their half-sister Sarah in 1798-1803, but there is no direct evidence for this and it is hard to square with Frances's affection and financial assistance to Sarah in later life.  Frances Burney's mother, described by historians as a woman of "warmth and intelligence", was the daughter of a French refugee named Dubois and had been brought up a Catholic. This French heritage influenced Frances Burney's self-perception in later life, possibly contributing to her attraction and subsequent marriage to Alexandre D'Arblay. Esther Burney died in 1762 when Frances was ten years old, a loss which she felt throughout her life.  Frances's father, Charles Burney, was noted for his personal charm, and even more for his talents as a musician, a musicologist, a composer and a man of letters. In 1760 he moved his family to London, a decision that improved their access to the cultured elements of English society, and as a consequence their own social standing. They lived in the midst of an artistically inclined social circle that gathered round Charles at their home in Poland Street, Soho.  In 1767 Charles Burney eloped to marry for a second time, to Elizabeth Allen, the wealthy widow of a King's Lynn wine merchant. Allen had three children of her own, and several years after the marriage the two families merged into one. This new domestic situation was unfortunately fraught with tension. The Burney children found their new stepmother overbearing and quick to anger, and they took refuge from the situation by making fun of the woman behind her back. However, their collective unhappiness served in some respects to bring them closer to one another. In 1774 the family moved again to what had been the house of Isaac Newton in St Martin's Street, Westminster, London.
Question: Why were Frances and her siblings upset about this marriage?

Answer:
This new domestic situation was unfortunately fraught with tension.