I think you can either establish parameters - "Yes, I will be your friend, but you cannot call every day, we can get together once a week" whatever you think you can handle, or you can say "Yes, I'll be your friend, but if you start talking about X, Y, or Z I will stop you, let's talk about life now ..." or you can just decide, if that would be to stressful to you, and she won't follow any parameters, to break it off again. Explain to her, if you feel you must, that friendship is a two-way street, and she needs to work at being a better friend, and so do you - by keeping yourself sane, but she needn't hear that last part.

If you don't want the effort, then I'd leave it alone. She obviously managed without you for those years, she can do so again.