I noticed that too. :\ I don't think it's ever been stated but she must have been born between 1978 and 1985 in order to be at Hogwarts during Harry's sixth year. 126.96.36.199 17:00, April 17, 2011 (UTC)
Between 1978 and 1984, actually. Harry's the only person who got on the Quidditch team at 11. Demelza had to be at least 12 to be on the team in HBP. --HarryPotterRules1 (talk) 23:12, February 9, 2014 (UTC)
Shouldn't it be,...
... "Demelza Robbins"? MinorStoop 12:25, February 16, 2014 (UTC)
Katie is in Harrys year too and shes on the team in all the movies