I think it's unfair for her to burden you with all the responsibility of making her feel needed - especially since you really aren't the cause of her insecurity. If she is suffering from C-PSTD, then she needs to take steps to make herself feel better with you helping her. Not expecting you to just inherently know how to deal with it.
Reading about C-PSTD, I don't understand how she can tell you to "figure it out". From the little research I did, recovery seems complicated and is approached from many different angles. She needs to tell you how to deal with it and what to do - I find it extremely selfish of her to expect you to muddle through her problems on your own. I'm not trying to be mean - I am aware that what she suffers from isn't her fault. But in order for her to recover or deal with it in a healthy way - she needs more than just you figuring it out.
With normal insecurities, I can understand - but something as complex as what she is suffering, what little you do won't really make a difference unless she makes an effort along with you.
All you can do is explain to her that you want to help. It isn't your fault if you don't know what to do, and if she wants to keep you to tell you what she needs. Because it's unfair for her to make you deal with her problems on your own.