When Boa was a queen her nation got involved in a war with another nation (Rapturia, a fallen nation whos people turned into zombie wasps). Near the end of her life a special forces squadron of Rapturia raided her palace and fought her. For the first time she was harmed and kissed the woman who harmed her without thinking mid fight. This gave the woman the chance to kill Boa and ripped her spine out with Boa's head still on with the look of a heart shattering. Her tomb was dug by the remains of her people and after the fall of Rapturia many years later a group of bandits including one of the Rapturians entered her tomb without knowing her past. Many decades later the realm of non existence was imploding on itself throwing out chunks of non existence to reality and the multiverse including Boa's tomb. When it was discovered her corpse that was still somewhat intact due to how dense her body is was moved to a lab where she was resurrected. Her spine was missing so Adeliné made a mechanical spine and put it in her skeleton before resurrection.
The reason for her being a masochist is because she thinks the only one worthy of bringing her an heir was whoever was stronger than her. This is also why she kissed a woman who ripped her spine out moments later.