Dunya Scheer (ドゥーニャ・シェーア) was first introduced in episode 13 (Isolated Pawn) as a woman soldier in the army of Disith.

The purpose for the introduction of this character was, originally, to "humanize" the forces of Disith as the story was preparing for a turning point of the plot, where the two opponents Disith and Anatoray will resolve to ally against the "great villain", The Guild.

In fact, until that moment, the viewer had never seen a Disith soldiers' face, as they, unlike Anatoray soldiers, wear protective masks in battle.
She appeared for the first time as one of the members of a small Disith patrol that captured Tatiana Wisla and Claus Valca while they were trying to reach into one of Silvana emergency resorts. The patrol actually forced them to put their head into the cannons of one of the resort's turrets, presumably as a way to stop this latter from opening fire against the Disith migratory capsules that were going to land nearby. When the capsules lands, the Disith patrol lost interest in the two prisoners, to ran towards the grounded ships, presumably to help the civilians - who were their fathers, mothers and sisters, etc - to get out of the dangerous artifacts.
When Dunya reached the landing field, she realized that the ship with the civilians didn't survive the launch - a launch failure of a civilian ridden capsule was shown in a precedent scene of the same episode- and she fired all the rounds in her weapon as a way to express her impotent grief.

Puzzled by the soldiers behavior, Tatiana and Claus followed her and watched her fall, realizing with surprise she was a girl pretty much of their age.

She is later involved as part of the ground force in the Disith operation to raze the Anatoray capital which is successfully completed. She is most likely evacuated when the Anatoray fleet offered its cease-fire and the Disith fleet withdrew.
We next see her involved in the same operation Mullin Shetland is involved in; they first meet when she falls over Mullin trying to catch a dove to eat. Over the course of their training, they meet several times and eventually develop a long lasting relationship.
A small scene during the training for this operation, where she defeats at arm-wrestle some Anatoray's Vanship pilots, seems to imply that she has a quite uncommon physical strength, but this is not openly stated during the rest of the series.

The relationship between her and Mullin culminates in Mullin asking Dunya if she would join him on the Silvana. Dunya accepts with the approval of other Disith soldiers and Mullin is overjoyed. The operation commences shortly thereafter and it is a success, but Mullin is gravely wounded and presumed dead. Dunya cries for him as she sees him and finds his Survivor Medals lying on the ground. No more reference is made to Dunya until the last episode where she is seen getting the message Lavie Head and Claus's fathers were supposed to have delivered over their new grave. She is then seen in the closing scene in a motherly fashion

Source: wikipedia