The `Never Been Kissed` actress and her art consultant boyfriend Will Kopelman - who she started dating in February 2011 - reportedly got engaged in Sun Valley, Idaho over the Christmas break.
A source - who revealed the ring is by Graff - told People magazine: "They are very happy together."
The couple are said to have first dated briefly in 2010 and reunited again in 2011 with Will besotted by the actress, telling friends last year that he was "madly in love".
A source said:"He`s madly in love and knows she`s The One."
Drew, 36, has previously been married to Tom Green from 1999 to 2001 and to Jeremy Thomas briefly in 1994 and enjoyed serious relationships with The Strokes drummer Fabrizio Moretti and Justin Long but has been "yearning to get married and have kids," with Will, 34, the son of former Chanel CEO Arie Kopelman.
Drew previously admitted she used to crave being in "crazy love", but has become attracted to relaxed partners as and romances as she has grown older.
She said: "When you`re young you just want to be in love. I call it crazy love, because you just want to have fun and you`re not thinking about the future or kids. You just want to have a good time with that person.
"Then, as you get older, even children aside, you just think, `God, I actually like when it`s easy, and I want these attributes from this person. I need these kinds of systems in place to feel calm."