Is this mare done growing?

I am currently looking to buy an OTTB. She just turned 3 on Feb. 23, 2011, is 16 hh, and only had two starts on the track. I asked for the owner's opinion of how much more she will probably grow and he said he can't see her growing not really any more than what she is now. I understand that growing is different for every breed and it depends on several factors as well (nutrition, genetics, workload, etc...), but she seems young to be completely done growing...any opinions?