"It was so wonderful but in a split second it was taken away from them. My brother [Rob] was on the scene in 20 seconds and performed CPR on her with others, including an off-duty police detective who was driving past.
"They tried for 45 minutes but she had died instantly in the impact. We all feel unimaginable pain and tragedy, our entire family is devastated."
Mrs Smart said Mr and Mrs Marsden met in 1999. They lived on a lifestyle block on Central Rd and she was a homemaker.
"My brother and Jacque loved each other so much. They hung out together, talked all the time.
"She loved cows and farms. After school while everyone went drinking in London she went on an exchange, working on a farm in Switzerland."
Mrs Smart said the family holiday encompassed the couple's love of mountain biking with family.
"They had an amazing time. Jacque was camera-happy, Instagram was full of all these pictures. They were having the best time, just perfect.
"It's just a shock."
She said the family wanted to thank the emergency services.
A service for Mrs Marsden will be held at the Clevedon Presbyterian Church on Monday. It is the same church in which a funeral was held for Mrs Marsden's mother, who died three weeks ago.