It isn't a bug, instead it is a confirmation you haven't done everything with her. For the scene to progress, you need:
1) Both you and her at 70 points each (done)
2) Repeat her scenes at least once AFTER reaching 70 points with her.
Option 2) isn't always right as some scenes can be played to completion WITHOUT reaching 70 points with her but just as a failsafe I recommend you do. Check the guide (link in the first page of the thread) to know which scenes you can do with her. Most likely than not, you're gonna be missing either the forced blowjob after you peek on her OR the footjob when you grope her at night.
Anyways, after you've done all of her scenes, the "Confront Her" option should lead you to the next step and have her fuck you.