100 years ago? This doesn't make sense. Bianca's mom has been present throughout the flashback, meaning this scene is likely her first meeting with her "mom" because I doubt regular humans could look that good while being over 100. So, Bianca's mom is not Bianca's mom and Bianca actually lived before the mutants existed (remember that scene on the train where the old man before the tower existed, before all these mutations existed) and survived through science.
OR I could be thinking too much and life expectancy has been extended with the use of science. But that's just a theory.