Family tributes to Millie, 12, and her brother Jackson, 17, who died in a crash on their way home from school, have been vandalised for a third time.
It included childhood teddies and tributes from a former teacher but the family noticed it had been damaged again by vandals on 10 November.
"I heard the ambulance and all the sirens ... my motherly instinct kicked in so I went off in the car to see if I could find out what was wrong and I was met at the bottom of the road by the police."
It took Mrs Grant five years to find the courage to visit the crash site and she said she did not understand why anybody would want to destroy their space.
"I couldn't face driving along this road ... and then it would have been Jackson's birthday ... and I finally made it to here to see exactly where it was and decided it's time for me to place my little memories here [at the memorial site].
"It wasn't easy but now it's a little place I can drive by, blow a kiss ... just come for special times ... it's nothing to anybody else ... why?"
"It's hard enough to have lost them but for this to be destroyed three times, I mean there's a heartless person out there.
"It's beginning to feel personal now, so all I can say is if you're out there have the guts to come and speak to me and tell me what your problem is."
PC Dean Wright from Wiltshire Police said: "This is an incredibly personal site for the family and to have it repeatedly vandalised has caused a great deal of distress.