Presumably they won't take up her references until after she has been interviewed, in which case I would strongly hope that the interview process would be robust enough for them to realise she is unsuitable.
I don't think they are asking for your thoughts on her suitability for the role (largely because they wouldn't assume that a personal referee would have the knowledge or experience to understand what they are looking for), they will be asking you how long you have know her and in what capacity.
If you think other people will be adversely affected by her attitude (sticking with your SENCo analogy, say) then you need to be honest. You could ring or write a covering note asking that they don't disclose the reason she didn't get the position - but they'd be under no obligation to pay any attention to that.
If no real harm will come of her being just a bit crap, then you could say stuff like "I've known X for 10 years in a personal capacity and while she is honest and reliable I am unqualified to comment on her suitability for the role".
In all honesty their decision will not hinge on your reference. It will be more likely that it is a cross check that the person is who they say they are. Or you could do what I did and said that my employer had banned staff from giving personal references in case they were mistaken as statements from the company
I haven't had the questions yet. Thing is, she really would be rubbish - think a SENCo that thinks ADHD is made up. She has a real blind spot that she thinks is totally reasonable, but which totally gets in the way of her realising her dream
Apologies for vagueness, but I think the precise details are outing, and the gist ought to be enough.
A friend wants to take up a voluntary role for which she needs some personal references. She has asked me to be a referee.
I think she is unsuited to the role, and can't in good conscience recommend her.
She would disagree with me about her unsuitability (obviously) and feel hurt by the suggestion. But I know I am not alone in my feelings as her lack of a key soft skill has been commented on (to me, not to her) before.
I have tried to address the issue with her gently before, but either I was too subtle or she doesn't think it matters.