Time

The reason she has caused you pain, is because her presence in your life has inadvertently resulted in unresolved issues of yours to surface. If you don’t address anything, it won’t matter in regards to whoever you move on to next, or even if you stay alone… your insecurities/deep-rooted issues will remain as they are and will show up whenever you meet new people.
She can probably improve on herself too, and if it’s time to move on then do that, but also try to think about your main problems with her and with yourself in that time period.

Otherwise you’ll keep going through new people like chocolate bars, throwing out the wrapper when you’ve “had enough,” not realising that you made the choice to allow them into your life, and that it’s also your choice to establish boundaries and expectations.

The more you know yourself, the more you know what you can handle, and what you want from others so that you can get along happily with them, and how to clearly state your needs/expectations so that there is no confusion or misunderstandings.

If you continue to have the same kinds of issues with new people as you did with your former friends/lovers, then the problem lies within something you’re doing wrong (because you can only control your own actions and not those of others). It doesn’t matter if THEY acted awful towards you… you can only tell them how they disappointed you and then forgive and forget, or improve your own behavior and raise your standards so that you won’t tolerate when people unfairly “cross the line” in the future (and show no remorse or consideration, etc).