She has something she wants to sell, and apparently, to you. But every time you suggest some independent inspection, she baulks.
I can't really understand why this is even a question. Me? I'd walk. From what you've said, at this point, nothing she could do would induce me to buy it, no examination, no inspection, not her getting brakes "fixed" first, nothing.
As far as I'm concerned, to buy from a friend requires a degree of trust, and everything done to date would undermine that. It's simply not worth the aggravation when, or if, it goes wrong.
Walk away. If you still want a car of that type, research it like normal and treat it with the scepticism you would normally in buying from a stranger, and buy a different car.
A few months ago I asked her to put the Mini through a full service (which I would pay for) to make sure that the car is 100% sound. She refused saying that it had only had a service last year and she was told that the car is in mint condition. At this point alarm bells started to ring, but I backed off and told her to forget I asked.
That, right there, is the point you slipped up. I understand why you did as you did, but the mistake, as I think you now know, was not either insisting on a full service (by YOUR choice of garage), on condition that you'll pay for the service work if you wish, but she pays for remedial work on faults, or not walking away when she refused.
To be honest, from your opening post, she is not coming aross as a friend.