The trial starts on Thursday in Vienna. Swedish Radio Östergötland spoke to the girl's lawyer Wolfgang Blaschitz.
"We are going to fight as she of course denies that she is member of ISIS," he said.
Asked if she has been in touch with people from the terror organisation IS, Wolfgang Blaschitz replied:
"No. With people from around the world connected in groups on internet, but it is not proven that these people she was talking to were members of a criminal or a terrorist organisation."
The teenager from Linköping was arrested at a train station in Vienna in December since her parents reported her missing, and had told police they suspected she may be on her way to Syria to join the terrorist group.
At the trial, the girl's family and representatives from the Swedish embassy will be present, as well as a social worker and representatives for the police's section working against international organised crime, Swedish Radio's local station in Östergötland reports.
Lawyer Wolfgang Blaschitz has taken on several similar cases in the past, but this is the first one with a suspect from outside Austria. When asked how she is doing Blaschitz said, "She is ok, and hopefully she will be released soon."