* Born in 1951: We know Bellatrix was born in 1951, as this is stated in the Harry Potter Wiki and is supported by the fact that she was in the same year at Hogwarts as Sirius Black (born 1959), who was 5 years younger.
* Battle of Hogwarts (1998): Bellatrix dies in the Battle of Hogwarts, which takes place in 1998.
* Age range of 46-47: Therefore, Bellatrix would have been either 46 or 47 years old at the time of her death.
It's important to note that while we don't have a precise age, this range is highly likely given the information we have.