Danielle Marsh, from Edgbarrow Road, will jump out of an aeroplane to raise money for British Heart Foundation.
The 19-year-old was inspired to fundraise for the charity after her granddad Peter Hadlow died in front of her last May.
She said: “It was just a normal, sunny Friday and me, nan and granddad went into his favourite café in the High Street.
“We did a little bit of shopping, went to the garden centre and back home again before granddad and I popped up to the local shops to get the paper and everything was just fine.”
However, on returning home, he clutched his chest and collapsed in front of me and my nan.
“I called immediately for an ambulance, shaking and terrified not knowing how I could help my granddad.
“They arrived and performed CPR.
“After what seemed a lifetime of waiting and not knowing, we were told by paramedics that sadly, my granddad had passed away and there was nothing they could do to revive him. My granddad, my best friend, was gone in a matter of minutes – this man was my soulmate, the person who I’d run to for advice; he always knew best.”
Mr Hadlow, who was 68, lived in Sittingbourne, in Kent, which was where he suffered the fatal heart attack.
Danielle has so far raised £624 for the charity.
She will jump from the plane at Old Sarum Airfield, in Salisbury.
To sponsor Danielle, go to www.justgiving.com/danielle-marsh01