Theodora was named after a great Byzantine Empress. In fact, all her siblings are named after major names from the Roman Empire. Her elder brother, Hadrian - one of the greatest emperors, and her younger sister, Livia Drusilla - the first woman who was Deified, and the first Empress of the Empire. The family was highly influential, and had high hopes for each of the Cromwell children. Hadrian was of quick wit, charm and charisma - going on to be an influential political figure in the Royal Scottish court. Livia Drusilla, of fair face and sparkling etiquette; was beautiful and courted highly, and thus married to a high ranking noble. This left Theodora - with the suitability of Livia's match and the success of Hadrian's endeavours, Theodora was left to do what she pleased, for the Cromwells had achieved all they really needed to retain their good name.
Theodora excelled in Hogwarts, being sorted almost instantaneously in Ravenclaw house. No one suspected it, she grasped concepts faster than others, and found solutions even faster. That and her seer bloodline (from her mother's side) gave her massive insight which she used to further her study. Needless to say Theodora flourished, especially in Divination, so as soon as she progressed through to seventh year, she knew what she wanted to do with herself - teach. As soon as she finished her seventh year, she took one year out to go into court, like all young ladies did, present herself to any bachelors and see if anyone wished for her hand in marriage. While she did receive offers, she turned them down. Her vision was clear, and she didn't feel like she needed a man's presence to be successful. Instead when she turned twenty, she applied to work at Hogwarts.
Initially she worked as a Matron, assisting the healer. After two years, she became Head Healer in the Hospital Wing. Three years passed, after her twenty fifth birthday she was given the role of Divination professor. For five years she taught, and when she turned 28 she was made Head of Ravenclaw house. It was not long then, two years, to be precise, when the previous Headmaster, a wizened and forgetful man, passed away. The clear candidate for his replacement was Theodora - she had been working at Hogwarts for ten years, and worked her way to the top. For two years now she has been Headmistress, and prevailed over the school quite formidably.