Ram met Seeta in the forest after Luv and Kush caught the horse of his Ashwamedha yagna. He met her in the forest. Valmiki asked Ram whether he would take her back and Ram says that he had sent her off once with a reason and so couldn't take her back. That's when Seeta says that when she was sent away for the from Ayodhya, she didn't give up her life because she was pregnant. Now that her sons were grown up and had met their father, she had nothing else to live for. She calls upon Mother Earth to take her in.