The official release date for Amelia is the end of August. She is (currently) available for preorders at PullipStyle, HERE.
Now, the original amount of dolls set aside for preorders already sold out last night (she went up for preorder last night) and PS opened up more dolls for preorder reservation. If she sells out again, that does not mean she's sold out for good! PS is a responsible shop and doesn't put their full run up for reservation so that they can do things like check over boxes and make sure all the dolls are pristine before they send them out. Because of that, more dolls will open up when she arrives in August and they know exactly how many good dolls they have to sell!
TLDR: If you need to save up and miss the preorder, don't despair, you'll get another chance at the end of August :)