The Loughborough athlete's jump beat previous holder Janine Whitlock's 2005 record of 4.47m.
Dennison's recent form suggested a good performance after she set a new British indoor record of 4.46m in February.
"I knew I was in good shape in training and I would have loved to have taken the bar higher," said Dennison.
The new outdoor mark is within the World Championships A qualifying standard. The World Championships take place in Berlin, Germany on 15-23 August.
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