Vichitravirya married only her sisters, because Amba told Bhishma that she had fallen in love with Salwa, and was not ready to marry anyone else.
According to the summary by C. Rajagopalachari, she resorted to penance and received a garland of blue lotuses from Lord Kartikeya and it was foretold that anyone wearing the garland would become the cause of Bhishma's death.