We were told it's intended for 16+. I do know someone who asked about enrolling her younger teen and was told she was too young. I think in the end she used some of the summary diagrams on healthy vs abusive relationships to have conversations with her child.
The charity have an email address, you could just ask. I know they do work in schools but I'm not sure whether that is also 16+. I'm fairly confident it's not the complete course, but samples / adaptations.
Ultimately, you should do the course yourself first if you decide to let her do it. Personally, I'm not sure I would set a 13 year old off to follow it on her own. It is in no way comparable to reading legislation - legislation is cold, impersonal and distanced. This course is up close and personal. Read the course book together, maybe, because you can discuss and contextualise and support. But only after reading it yourself first.
Some of the examples are upsetting as an adult, in particular the sections on sexual abuse and the effects of abuse on children. I wouldn't want a 13 year old reading that and I certainly wouldn't leave them to read it if I hadn't read it myself. It's distressing.
I don't think it would demonise men, that's an unhelpful characterisation of the course. It discusses patriarchy and misogyny in terms of how those parts of our culture perpetuate abuse - victims are conditioned to accept it as normal, abusers feel entitled to abuse, observers turn a blind eye. It doesn't suggest that "all men are abusers". That would not be helpful.
What distressed me was being confronted by the deliberate nature of abuse, the reality of how much suffering humans choose to inflict on one another, and how many were suffering. It was easier when I thought it was accidental and only happening to a few of us. The course includes examples of real abuse and real suffering, in detail. (I have read legislation and the other types of materials you mention - not the same at all, not even close.)
All examples used in the course happened to multiple people (because if they used examples that had only happened to one or a few it would risk their safety and privacy), so that means the acts you struggle to imagine anyone perpetrating were thought up independently by multiple abusers and inflicted on multiple victims.
It's not easy to come to terms with. I'm not convinced it's a good idea for a 13 year old child to be given that level of detail - is a child developmentally able to digest it and apply it with the judgement required or is she just going to lose trust in people? Or hold a simplistic view ( "oh, this is my checklist of warning signs, if someone doesn't do xyz actions then it can't be abuse" ) that leaves her at risk herself? She's still at an age where things are quite black and white, which makes seeing and interpreting the dynamics and nuances difficult.
Of course, it does also cover healthy relationships but for a child without a facilitator running an in-person session to put things in perspective, I would be concerned about the darkness clouding out those aspects. Again, will she be able to understand the dynamics and nuances? See the distinctions and understand them? Process the grey spaces? Not so sure. We feel grown up and wise at 13 but that's not the same as having an adult's understanding of things!
We pretty much always recommend doing the course in person (pandemics aside) because you don't take the same from it alone without a facilitator and without any discussion. I think that would be even more the case for a child - the work they do in schools is discussion based.
I would contact the FP team and have a conversation. They've always been helpful and approachable when I've made contact with different questions.