You were desperate to escape the torturous fate your father was forcing you into. A marriage into a family where you'd be locked away and used only to bare heirs. You didn't wish to be wed, let alone into a life of marital slavery.

When you had left to visit Illyria one last time, you concluded that perhaps no longer being 'pure' would save you from the lifetime of misery. You wanted your first to be with someone you could trust, but equally you were now limited to laying with an illyrian. So you decided to ask one of the few illyrians you knew and trusted, Cassian. He knew of your situation and as a young hormonal male himself he was more than willing to oblige, plus you knew he'd remain respectful and kind.