Rosie O'Donnell's daughter Chelsea -- who went missing on August 11 only to return a week later -- has left home again ... this time to reunite with her birth mother, Deanna, who gave up Chelsea for adoption in 1997.
According to our sources, Deanna drove down from Wisconsin to pick Chelsea up on Monday afternoon ... which happened to be her 18th birthday.
We're told Chelsea and Deanna drove back to Wisconsin, where Chelsea will stay for the time being.
We're told Rosie advised Chelsea NOT to go with Deanna, but she went anyway. We're also told Rosie has cut off Chelsea financially and has refused to turn over her birth certificate and social security card.