This really mirrors what the girls and I have been working on for years. I agree and preach that if you stay out of trouble your rarely ever in trouble but on the off chance I want them to have options.
It is really encouraging to hear that - it's one thing that I don't hear nearly often enough, especially in the United States.
From my limited experience, "options start between the ears", and are increased or decreased within distance and time constraints. They nearly always narrow in scope of availability from a wider array of passively active nonverbal (Locking eyes with someone and making sure that they know that you notice them, as an example), or verbal de-escalation and non-kinetic less-lethal options to a handful of definitive, nearly certainly life-altering and damaging kinetic options. Less distance and less time means greater likelihood of definitive violence as the solution to what is likely already a violent problem.
Y'all have given me some great ideas to look at. I'll be going over them with my daughter and sort out a carry method. Right now I'm thinking about how to carry it using the chest strap for her HR monitor.
This is a great idea, and possibly looking into a way to secure a "neck knife" to a running chest strap in a manner where you won't experience the knife flopping around, and also holding it securely in a good sheath could be the ticket.
I would encourage you all to practice drawing the knife and conducting pinning/breaking contact under from many positions under stress, as a weapon that isn't accessible when you need it most is useless at best, and a liability at worst. Similarly, understanding the capabilities of a blade dictates usage: as ugly as it sounds, knowing when it is better to commit to the fight and when to create an opportunity for breaking contact and solving the problem with pure footpower and making noise. The difference in approach is highly contextual, and something that must be learned and experienced. The one emphasis that I place on both approaches is that once you make a decision, you must commit to it - there is no going back, no second-guesses, and surely no do-overs. Anything short of full commitment will likely result in severe injury at best.
I do personally prefer a solid AIWB setup to a neck knife in terms of one-handed accessibility under stress because of near immediate accessibility, but everyone's needs are contextual, and there is no wrong answer if it is proven to work within your requirements and parameters, and gives you a desired result.
Hope that this helps.