Muggles' Guide to Harry Potter/Characters/Demelza Robins

Overview
Demelza Robins joins the Gryffindor Quidditch team as a Chaser.

Half-Blood Prince
Demelza Robins is one of three Chasers that Harry puts on the Gryffindor Quidditch team after a series of try-outs. The other two are Katie Bell and Ginny Weasley. This seems to be something of a tradition; in Harry's first through third years, all the Gryffindor chasers were girls as well.

A little later, she delivers a message from Professor Snape to Harry about a detention.

Amongst the team changes due to illness and detention, Demelza is the only Chaser who plays against all three other houses. Katie Bell is sidelined by a cursed necklace for two matches, and Ginny becomes Seeker when Harry is put into detention by Snape.

Deathly Hallows
Demelza is mentioned in passing as being one of the defenders in the battle at Hogwarts.

Strengths
Demelza is quite adept at Quidditch, having a knack for dodging Bludgers and for making tricky shots. She is known to work well with the other Chasers and is friendly with the Beaters. Other than her Quidditch ability, Demelza's strengths and skills are largely unknown. She fought in the Battle of Hogwarts and must have been both brave and cunning to do so as Professor McGonagall was not allowing underage students to take part. This she seems to have ignored, as did Colin Creevey, proving bravery and a possible disregard for rules. We note in the Analysis section, below, though, that she might have come of age during the year, and so be allowed to stay at Hogwarts.

Weaknesses
Like her strengths, Demelza's weaknesses are largely unknown. However, it can be noted that she is rather sensitive, succumbing to tears on occasion, generally because of Ron.

Relationships with Other Characters
Demelza is rarely seen outside of Quidditch games, where her relationships would be on a teammates level. We don't see enough of her outside Quidditch games and practices to get any feeling for how she would relate to other students.

Analysis
In the Strengths section, above, it was noted that she likely was underage at the time of the battle of Hogwarts, and so would have been fighting without permission. We have no information about her age, except that she is, we must assume, younger than Harry; if she was older than Harry she would have already left the school by Harry's seventh year, and would have had to be returned to the school somehow in time for the battle. If she had entered Hogwarts the year after Harry, she would be in her sixth year at the time of the battle of Hogwarts; and as Ron and Hermione did, it is possible that she could have had her seventeenth birthday between the start of school in September and the Battle of Hogwarts in May. If she was of age, then she would have participated in the fight with permission.

We note that, whether such was her intent or not, the author seems to have introduced Demelza in the same manner as she introduced Romilda Vane, possibly intending Demelza to be part of the group of girls centered around Romilda who are entering their fourth year as Harry is entering his sixth. This would make Demelza a fifth-year student at the time of the Battle of Hogwarts, and thus definitively underage. However, we must stress that this is a very tenuous line of reasoning.