The TV presenter has been careful to keep the 10-month-old out of the public eye – but she couldn't resist sharing a cute snap of her little girl as she played in a cardboard box.
The model-turned-campaigner, who recently announced her engagement to Belle's father James, told her Instagram followers: "Picked up all my parcels and post from work.
"Luckily have my little helper to open it all!"
Katie gave birth to Belle in March, after revealing she never thought family life would be possible for her because of the appalling acid attack which scarred her for life in March 2008.
Katie, now 30, suffered severe burns after a man hired by her ex-partner threw sulphuric acid in her face.
Since the attack, Katie has had more than 100 operations and has campaigned tirelessly for more help for burn victims.
After giving birth to Belle, Katie said: "To have had my own life saved in hospital and then to be there giving life to this precious little person, I thought, 'This is why, this is what it's all about'."
Talking about becoming a mum, she said: "People used to say to me, 'It's a love like no other,' and I understand that now. She's so precious and I just feel so incredibly blessed to have her. She's our world."
The former model had been unsure whether she would ever be able to conceive after what she'd been through.
She said: "I already felt grateful that, after the attack, I'd managed to restore a life, have a job, friends, a social life, and I thought, 'You can't expect to have everything, this is enough'.
"Then, to meet and fall in love with James, a man I knew I wanted to have a baby with and who makes me so happy, and now to have Belle - it's just amazing.
"Most of all I want her to be happy. I thought I knew, after all that happened to me, what happiness meant, but having Belle has shown me what true fulfillment is."