Little 12.2 cob filly?

we are about to get a 10mth old heavy cob filly. She stands at 12.2 at the moment but as she is a rescue there is not breeding info with her. What size should she grow to ? at wot age do they stop growing and start filling out ? Any name suggestions would be great too. She is like a mini clydesdale bay in colour with four white socks and a mainly white face (a very sweet face) black mane and tail. Thanks