Video conference call - unable to see other person

Hi,

Today I first tried teamviewer and I tried to do a video call with someone. During the video call I could hear the other person but I could not see her. She told me she was able to see herself and that her webcam was definately turned on. She was able to see me and hear me and I could also see myself. We tried to call several times but still I could not see her. Is there a way to solve this problem? 

Thank you in advance