Determined Lydia Crawford, who is nine, donated some of her hair, swam a mile and held a cake sale to raise money for the Little Princess Trust.
The charity provides free real hair wigs to boys and girls who have lost their own hair through cancer treatment or other illnesses.
Lydia, of Bulkington, heard about the charity and following the death of her grandfather, Chris Tapliss, 67, last October.
Mr Tapliss, of Melksham – who called Lydia “his little princess” – was a swimming coach and Lydia loves to swim. She is a member of Trowbridge Amateur Swim-ming Club and trains every Sunday. She set herself the challenge of swimming one mile in 64 lengths of the pool.
She completed it last Thursday, in 45 minutes, and could have carried on.
She said: “I didn’t find it hard at all. I normally do 50 lengths in half an hour. I did have to pace myself.”
The next day she had her hair cut at Tops salon in Melksham. Her blonde locks were below the base of her back but she had 10ins off.
When she returned home, she baked cakes and biscuits – helped by younger sister Georgia, six, and mum Clare – for a coffee morning at her home on Saturday.
Friends and relatives also brought biscuits and the event raised £180. Lydia, a pupil at Keevil Primary School, had set a target of raising £350 for the Little Princess Trust but has so far raised more than £800.
She said: “I’m really happy about the amount. I think it’s a really good charity.
"When children get their wig they must be so amazed and happy because they have been without hair for such a long time.”
Mrs Crawford said: “Lydia wanted to do something to make her grandfather proud. She heard of the Little Princess Trust and that Jessie J had her hair cut off and came up with the idea of a sponsored swim and coffee morning.”
To make a donation to Lydia’s Little Princess Trust total, see www.justgiving.com/ lydiacrawford