"I think she would be completely overwhelmed and completely over the moon. She'd be going 'woo hoo', excited," Nicola Short told the BBC as donations on Claire's Just Giving page close in on £800,000.
Nicola added that Claire's family have also been given some small measure of comfort in their darkest hour by the donations that have poured in.
"Obviously they are extremely devastated but they're together, they are a strong family and they are close, they have spent all week together round at Claire's mum and dad's house," she added.
"Obviously the more money that's coming in is overwhelming but it is giving them a little bit of comfort to know she has managed to do such a great thing.
"I don't think any of us had any idea of how much she would raise."
Claire's parents Paul and Cilla released a statement earlier in the week echoing Nicola's comments.
"We are all devastated. It’s a total shock because she was such a fit girl. We’ve no idea what caused her death," the statement read.
"Claire was a bubbly, beautiful girl. She lived life to the full and was so determined.
"Claire has raised thousands of pounds over the years for charities. She was that sort of person.
"On behalf of Claire's family and all those who knew and loved her - we would like to say thank you so much for everyone's support.
"Claire would be so happy and overwhelmed with the incredible support that has been offered by thousands of people from all over the world."