1) What does "planted" mean in "she planted her rea end on the floor"? - does "Rear end" mean "bottom"? What does "planted" mean in "I planted myself and was about to tell her to get lost"? - what does get lost mean here?
yes, rear end is the bottom, what a person sits on. It suggests she sat down to stay. To plant oneself suggests to stay there with determination. Get lost means to go away, to stop bothering someone
2) does "blasted" mean "ran fast" in "she blasted past me"? Yes
3) What does "flash" mean in "flash her help"> Not sure, seems incomplete. Context?
4) What's "crusty heap" in "Juli left her socks in the crusty heap on our porch"? The heap is a pile her socks made when she dropped them. Crusty is an adjective that means the socks were dirty, sweaty, worn a log time and/or generally disgusting.
5) What does "wedge" mean in "I wedged myself up on the top shelf of my closet"? It means to squeeze into a tight space.
Hope that helps!