The singer-turned-designer contracted septicaemia after the loss. She has since become engaged to her partner Sam Cooper.
Speaking on the final episode of Channel 4's From Riches To Rags, Allen said: "I got really ill after he died and I was admitted into hospital. I couldn't have cared less if I was on my death bed.
"It was amazing how my friends reacted so much more to me being ill than to actually what I felt was the devastating part."
She added: "Even though what's happened to me has been beyond devastating, it's made me realise what I really have. I probably feel more compassionate towards things than I have previously.
"I spent a long time in a hospital bed and my outlook has changed. Everything has changed. I can't believe how much of my life I spent complaining about things."
Allen this week hit out at the person who leaked her Save the Date card confirming the day she will marry Cooper.