You don't have to tell her that you know. Just be accepting and validating of her emotions, whatever they are at the time, and be someone she can talk to. When parents have issues, our kids tend to get it both genetically, and they can be affected by what they experience or witness. We might not have been as available for them in many ways, or able to provide the nurturing and validation and open communication that would have been ideal. But we do the best that we can. Maybe letting her know that you are willing to answer any questions she has, about you or life in general or anything else would help. Just be available and willing to communicate openly and honestly, and be accepting of who she is and what she thinks and feels.

You can do it, and SI isn't the end of the world. She has professional help available too, right? If not, maybe you could find someone and just let her know that there is someone else she can talk to.