Yet the eight-year-old has an incredible zest for life that makes her feel as free as a butterfly, and led her to raise £360,000 so children like her could feel the same way.
Despite being confined to a wheelchair and needing help with every physical aspect of her life, Tilly manages to pack more activities into her spare time than most children could dream of – from ice skating and ballet to rock climbing and sailing.
Her amazing achievements have astounded her parents, who were given the devastating news that she had the life-limiting disease Spinal Muscular
Atrophy just after her first birthday.
Thanks to the charity Cauldwell Children, she was able to get the £20,000 state-of-the-art wheelchair she so badly needed.
The chair has not only made caring for Tilly far easier for her parents and helpers at the mainstream school she attends, but it also gives her the freedom to drive herself around and take part in all the activities she loves.
And having the chair inspired Tilly, of Leek, Staffordshire, to launch her mission to raise money so other children could have a chair like hers.
Together with her sister Candice, 10, she made a beautiful collage of butterflies to be auctioned at Cauldwell Children's charity ball. She amazed the hundreds of assembled guests by going on stage to tell them she had made the butterfly picture because her wheelchair had made her feel "as free as a butterfly".
"All I want to do is to give another child the same experience as I had when I got mine," Tilly says.
To her surprise, a bidding frenzy broke out and the collage even outsold an original signed Picasso etching in the same sale to make £360,000 – enough to help 18 other children.
Tilly's mum Jackie says, "The chair helped her go from being a bystander to someone who gets 200 per cent out of every day of her life.
"There is nothing she feels she cannot do. She will look at something and say, 'How can I do that?' and then find her own way. "We prayed she might be able to raise enough for one chair, but we were all amazed and thrilled with the result.
"There have been some very dark times for our family, but Tilly and Candice have brought light into our lives."
Cauldwell Children Chief Executive Trudi Beswick says, "Tilly is without doubt a true inspiration, not only to all the youngsters she meets, but also her peers. The courage and determination she shows on a day-to-day basis is overwhelming, compelling and inspirational to us all."