My 4 years old daughter attaches a lot of importance to toys, clothes, presents ... How do you help your kids take some distance with that ?

Sample behaviour I'm uncomfortable with :

* asking grandma "what present did you bring today ?" (she comes most weeks with a small toy or stuffed animal)
* taking a toy from her younger brother by force
* crying very loud when she can't get an object from the house or choosing the colour of her clothes in the morning (she is apart from that very sensible and we can discuss most other topics)
* insisting on sleeping with 15 stuffed animals & dolls in the bed and a dozen books at hand