You don't provide much background information (and if you're just looking for a general answer then you don't really need to get that personal anyway, especially on a public website) but this could range anywhere from normal attachment to compensation for an unstable home life to an outright disorder on the scale of "object sexualism" like this woman has:
As is mentioned in that article, it could also be a sign of Asperger syndrome.
If you can think of reasons that your daughter might feel insecure (recent move, change of schools, parental separation, loss of a family member, etc.) then her fears about that might be manifesting themselves in the hoarding behavior. If you suspect that she might have Asperger syndrome, you might want to speak to a specialist for a proper diagnosis and advice on how to prevent it from becoming a problem (children with Asperger syndrome are often highly intelligent and as long as the situation is identified early then some of the problems with social adjustment can be avoided altogether.)
It might also simply be a mild form of compulsion that can be dealt with using techniques like extinction therapy -- basically, you'd condition your daughter to accept the loss of these "special" objects by working up gradually from the least important of them and eventually exposing her to the (possibly just temporary) loss of things like toys or favorite stuffed animals.
Without knowing more about the situation, it's hard to tell if this is just a minor issue or is seriously compromising her ability to function (such as freaking out if a candy wrapper is thrown away, or being unwilling to leave the house for fear of losing some of the items) and the route you decide to take greatly depends on the severity, since an approach like gradual conditioning using extinction therapy could be greatly harmful to the psychological well-being of a child with Asperger syndrome, for example.