This sounds like a really stressful time for you, as well as for your family. It's really great that you've reached out for support here.
I think that your idea to have a chat with her counsellor is a good instinct. They may then decide the best way to bring up the topic of self-harm with her, based on their training and experience. They may even recommend that she see a psychologist, if they do not feel they have the right tools - this is a conversation you might raise with them if you are unsure of their experience.
I think that having a call with the suicide helpline - 13 11 14 - could also be really helpful for you. They are likely to know of and be able to share with you things that you may be able to do around the house to reduce risks, conversations you could have with her, flags to look out for, and more.
It is really important that you and your husband take care of yourselves as well. This can be a heavy thing to deal with day-to-day, and it's easy (and perfectly understandable) to become burned out. Even though it may sound difficult or unproductive, doing some things for yourself like yoga, meditation, going for a nature walk or swim, etc, make such big differences. These are also things that you might like to invite Miss 13 to do with you, which may provide a space for her to open up to you, or at the least, may help increase endorphins and be a nice distraction for her from what she may be feeling.
Please come back on here any time you feel like it could help, even if it is just to vent your feelings.
All the best to you and your family,