Its really difficult to say as pure draft horses (heavies) don't stop growing until they are 6 or 7. Heavy horses do most of their growing in the first 2-3 years and then the rate slows down. As she's a cross breed, you really can't tell what her final height will be as it depends on her parents and how tall they were. One thing you can be sure of, she will be be a large horse. Mares tend not to grow as big as the boys but who knows. Its going to be a waiting game. Just enjoy and love her until she stops growing.