Sorry for the really late reply, I hope you're doing better, and that things have kinda sorted out. Honestly, I think you're going through a normal phase of teenage years (identity crisis, etc.) For your first part written in 2010, I don't think there's anything wrong w/ you, nor do you have any kind of syndrome. I feel for you, in that I'm your age, but have always felt attracted to both guys and girls.
I've heard many stories from an older relative that told me of how les and bi women that have hit on her all had a rough past or complicated relationship w/ their father/mother. Ex: girls who've grown up w/o a mother in their life might have a need to fill that female-caring need w/ other girls. By the sounds of it, you become attracted to ppl who care for you in your life; to me, it just sounds like you need someone to care for you, give you attn, and love you, be it male or female. It doesn't necessarily mean you're bi.
That ties into your complication w/ your girly girl friend. She gives you an opportunity to fill that need for love and affection. Since I don't know your friend personally, I can't give a sound judgement, but from what I pick up from your side of the story, it sounds like she is either misunderstanding you and your feelings, or she's being insensitive.
The fact that you two live so close, and that you have that tomboy-ish feel, doesn't help. (I've noticed sth w/ myself; when I'm hanging w/ mostly guys, I act more feminine, and when I'm hanging w/ mostly girls, I act more dominant and masculine - does that also happen w/ you?) Scenario 1: she's misinterpreting your tomboy-ish aura + actions of care w/ ok signs for a romantic relationship. Maybe you just need to be straight-up and tell her you're not ok w/ this. Scenario 2: she knows you're uncomfortable, but being the girly girl who's probably on rebound, is flirting w/ you and having fun. She doesn't care that you're uncomfortable, she wants sth for herself, and will prob try to presuade you into thinking her way as well. Maybe you situation is a mix of both scenarios, w/ you kinda encouraging her on since you're curious too.
Why am I writing so much for you? You're relationship w/ your friend is very similar w/ a good girl friend I had. I cut-off our relationship, maybe too harsh and cold, cuz down in the core, I realized that although she came crying to me and asked for my help and care, she didn't want to accept the help or fix the problems, only cover them up; she cared for herself first b4 others, and that she had no idea how much I cared and loved her. Which I still do, but I watch her w/ a sad heart from a distance, and hope that she'll find someone who will love her. It just hurts to watch a friend consciously hurting themselves, and not wanting to fix the issue from the stem.
This relationship also had me wondering if I was straight or bi, since I was attracted to both genders. Her hinting at how I would be an awesome and good looking bf didn't help either. But that's enough personal crap from me. Let's get back to you.
My advice: don't stop looking for that right guy/gal, even if you have to go through a few rough relationships. But to save yourself from further emotional hurting, which you've gone through quite a bit from an early childhood, don't let yourself go into a state of "this is good enough". I don't think you should date your girly girl friend. Not until you're sure it's worth it. In short, don't sell yourself short! You're well worth it
Well, that was LONG!! @_@ Let me know how things turns out/ turned out, but keep in touch if you need support! Iunno why, but I now feel the need to help you through w/ this!!