Eleanor was lost for words and hope upon hearing Astrid's desperate cry to protect her daughter. It was true Diana was not a Silverheart. Astrid had done something rather stupid as retaliation after her marriage to Eris.
She didn't love the general and still doesn't till now. Her heart was cold due to her foolish obsession as some would call it. After her wedding night with Eris, they had consummated the marriage. Eris was called to war; it was an emergency summon as the kingdom borders were being compromised, leaving his wife, who didn't want anything to do with him.
Astrid, during her lonely night, drank herself into a stupor every night and visited special brothels that rendered services to noble ladies. This continued until the grieving princess found entertainment with beautiful men who reminded her of her obsession. When she found out she was late.