Johanka was originally an inhabitant of Silver Skalitz.
It's hinted that she harbored feelings for Matthias, interrupting a fight that he is involved with and insisting that she needs to see him when she heard of his broken arm.
During the attack of Skalitz by King Sigismund, she managed to escape and fled to Sasau, and can be found at the Sasau Monastery where she treats the refugees of Skalitz alongside Brother Elias and Brother Nicodemus in the Sasau Infirmary. She asks for Henry's help treating her patients during the quest In God's Hands.
The Sasau custodian, Baron vom Berg, is infatuated with Johanka, and visits the infirmary frequently in an attempt to woo her. Johanka is initially annoyed by his advances, but asks Henry not to interfere, adamant it will only make it worse. Later, she admits there is something about the Custodian she likes, and reveals that she feels some level of resentment towards Henry for not being there, when the Custodian was. Nevertheless, she is grateful for Henry's help.
During Pestilence, Henry comes to Johanka to ask for her help in curing a plague that is ravaging the village of Merhojed. She is very concerned about Matthias, and advises Henry to speak to Brother Nicodemus. The two men are able to determine (with varying degrees of success) what the cause of the pestilence is, and Johanka accompanies Brother Nicodemus to Merhojed to assist him in tending to the sick.