Alya is a minor character in Rise of the Tomb Raider. Jacob was her lover, a fact that brought some inner turmoil to Jacobs feelings, as he sees his loyalties first and foremost with his people and not with his family. Together they had a child, Sofia, who after Jacob's death becomes leader of the Remnant.
Not much of Alya's life is known. The only time we get some background information on her in the game is in the Pages of the Ledger document set. Assuming that Sofia is in her late 20s and Alya was about the same age when she had her she was probably born in the 1960s or 1970s. Between Sofia's birth and the Events in Rise of the Tomb Raider she died, possibly during the revolt against the Soviets.
Alya is mentioned by Jacob a few times in passing, but he gives no further substantial information about her.