Background
I broke up with my ex about some years ago. I've been through a lot all those (many) years I was in a relationship with her, due to the fact that she suffered from various disorders such as depression, anorexia and OCD. Just to be clear I don't blame her for having those issues - and I helped her through the end - but because she wasn't a good person overall and she constantly tried to take advantage of her situation in order to make me and her family guilty, so that she could take what she wanted - mainly attention and money to buy unnecessary stuff and have plastic surgeries.
So after all those years in which she was practically extorting money off me, she still owes me. She gives back small portions but often postpones it, because she wants to buy more things. I've been in countless arguments with her, but to no avail. This makes me really upset, not only because I need the money back, but also because I really want to cut ties with her, as I really don't like having to talk to her every now and then. I also have a serious relationship and my girlfriend isn't happy with the situation. I asked her to put the money in the bank directly which she didn't, making all kinds of excuses and further delaying the payment because, by the time I asked if she did, she had already spent it all. I've talked about it with her brother, who still thinks of me as one of his best friends, but she doesn't listen to anyone.
Question
I don't know what to do to make her pay back the entire amount, or even pay me the portions when agreed. How can I persuade such a difficult person to be consistent with her obligation towards me?
Note:
I've considered stop requesting the money back, I just asked this question in case someone can give me some advice I haven't thought of yet, so this situation wouldn't end up so unfairly.
I can't afford to take this to court, nor I think I have enough proof in order to do so.
I live in southern Europe if that helps. Things are pretty loose around here and the minimum amount of dept that sends you to prison is quite big - but still less than the amount I'm talking about.