Whilst Isabella was a talented musician who composed her own music and played the violin beautifully, Maria Christina was noted for having a particular talent for painting. The two very quickly developed an intense bond and despite living in close proximity, wrote to one another constantly. Luckily for us, some of their letters, most of which demonstrate a bond that goes beyond sisterly affection, have been preserved and published in various books and journals. In one letter Isabella writes, “I am told that the day begins with God. I, however, begin the day by thinking of the object of my love, for I think of her incessantly” whilst in another she writes, “I am madly in love with you, virtuously or diabolically, I love you and I will love you to the grave”. It’s often been suggested that Maria Christina’s feelings were less intense than Isabella’s which is entirely possible. However, we cannot be sure as Maria Christina’s letters were all destroyed after her death. In one letter between them, Isabella herself questions the depth of Maria Christina’s feelings, writing “I cannot bear waiting to know my fate, and to learn whether you consider me a person worthy of your love”. Blinded by his own infatuation with her, Joseph remained unaware of how intense the relationship between his wife and sister had become; he also initially remained unaware of Isabella’s increasing melancholy. When he did realise the full extent of her struggles, he had no idea how to help her. Over the course of their three-year marriage, Isabella’s melancholy worsened, no doubt exacerbated by two miscarriages, an increasing dislike of sex, a difficult pregnancy and the traumatic birth of their daughter Maria Theresa, a hatred of the strict formality of the Austrian court and the death of Joseph’s other sister Johanna which only furthered Isabella’s obsession with death.
Ultimately the story would have a tragic ending; whilst six months pregnant Isabella was diagnosed with smallpox, which caused her to go into labour prematurely and on the 22nd November 1763 she gave birth to a daughter who died shortly afterwards. Her final act was to name her daughter Maria Christina. Isabella died less than a week later. Both Maria Christina and Joseph were heartbroken; the latter seemingly never recovered and for some time afterwards refused to even consider remarrying. Even after he did, he made it clear Isabella was the love of his life. Maria Christina also eventually married and had a long seemingly happy marriage.
During the course of their relationship, Isabella and Maria Christina’s closeness was noted upon by their contemporaries although they were not explicitly accused of anything, until after Isabella’s letters became public. The letters are a fascinating insight into what was at a bare minimum unrequited love but may very possibly have been a great love story between two brilliant women, born into a society not ready for a relationship like theirs.