When Claire Squires, 30, began the marathon on Sunday she had raised £500 for the Samaritans, who her mother Cilla had volunteered with for more than 20 years. Today the figure surpassed £1million and more than 68,000 well-wishers had been moved to donate on her JustGiving webpage.
The news came in a tweet via the online fundraising community.
Claire will be be buried next Wendesday alongside her brother, Grant, who died in 2001 aged 25.
Her friend Nicola Short climbed Kilimanjao with Claire two years ago.
She appeared on BBC Breakfast this morning to pay tribute to her friend:
Obviously [her family] 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.
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. I think she would be completely overwhelmed and completely over the moon. She'd be going 'woo hoo', excited.
Miss Squires was the 11th participant to die since the event began in 1981.
She collapsed in Birdcage Walk, near St James's Park, on the final stretch of the 26.2-mile course.
She died with the finishing line only one bend away, after 25 miles of the marathon.