Thank you so much for the additional details. With what you have added, to answer your original question to start, yes, I do believe she is still "into you" and is interested in you. And like I had guessed, you confirmed that she has trust issues. When you wrote back and said that she gets asked out by other guys, do you know if she does go on dates? You said she has male friends, but do you think any of the times she spends with these male friends could be considered "dates"?
Additionally, if she is getting so upset at just you adding a female friend on FB that she has to "unfriend" you, of course that indicates a high level of jealous. And of course, a high level of jealousy indicates that while she is definitely interested in you in a romantic way, she is also insecure. I know I am not telling you anything new with that. However, what MAY be new is that I think if you two would be willing to sit down and be very open, up front, and honest with each other, you could work on a romantic relationship. You both have the feelings, and you have history, which indicates from what you have shared that you are friends and get along pretty well. So given these observations, now the real thing that is standing in your way is trust and insecurity. And if you can show her that you ARE trustworthy, that you are NOT going to bail on her every time you have a disagreement, then I believe you have a really good chance. The key or challenge is going to be "showing her" that you are trustworthy.
What I mean by the above is that even though you have history together, she is still very vulnerable because of past relationships that, as you have indicated, "never work out." Unfortunately as humans, we are ALL influenced by our past relationships. If most or all of our romantic relationships have ended badly or been very short, then our expectations of future relationships do not have a lot of hope. That is, people who have had more drama and "bad" relationships are very likely to assume that the next one will be the same. When we go forward with this assumption, even though we probably do not mean to, we are a lot more likely to "sabotage" the relationship. In other words, we will unintentionally start exhibiting behaviors we exhibited in prior (bad) relationships because that is what we are used to. In turn, our relationship partners will react to those bad behaviors, and then we will continue in a downward negative spiral until the relationship ends poorly. This effect is known as the "Self-fulfilling Prophecy".
So again, it is important to recognize this history of behaviors on her part (and yours if you have done this). Once you acknowledge this, it is much easier to move forward. But many couples do not acknowledge this and therefore basically are "destined" to fail. Does this make sense? Let me know if you would like more clarity on this. But for now, my best recommendation is really sit down and explore her past relationships, what she has done, how she has acted, and figure out that she cannot continue to act in certain ways in your relationship if she wants the two of you to have a good relationship. And likewise, you have to commit to her to try hard to also not let the past experiences influence and impact how you communicate in this relationship.
Do you want to talk on the Phone or Skype? Please let me know if this is helping.