No, “Your” is not the same as “You are”.
You’re = You are.
So “Your a very good girl” is wrong.
Also, using an apostrophe in yours (your’s) is incorrect, and you should never use it. (we should never write “your is” as well)
What Mak_786 has written in his first sentence is correct (with a space between very and good). Or BillW’s last sentence:
You are a very good girl.