I am a little ashamed to say that I have been on both sides of this. When I was in her position, it was never a matter of wanting control or wanting to string someone along, but it was pretty much entirely about HUGE insecurity and the super attractive prospect of having someone (even someone you never actually plan on being with) that likes/loves you, finds you attractive, etc. At the time, I was young and very insecure, and it wasn't until I grew up that I realized how horribly unfair I was being with this behavior. All I could think about at the time was how I hated myself and felt no one around me valued me or cared about me, so behaving this way even with no intentions of following through made me feel wanted and special. I never actually planned on being with this person, even though he was crazy about me, but I had many of the same behaviors she has been exhibiting: constant texting, flirting, suggestive pictures/messages, etc. I liked knowing that I was only making him want me more and more because it made me feel desirable. You know her, and if you say that she is a genuinely good person, I believe you. I know I am not a bad person but I definitely did some harmful things during a time of great insecurity, doubt, and low self-esteem. Based on her history and situation with her orientation and the judgement and hiding she's doing, plus her own judgement and guilt about herself, I'm better she's doing the same thing I was doing. I can't tell you what to do, but I can tell you what I would do in this situation having experienced it from multiple sides: I would get out now. I know you love this woman and have a history with her and feel close to her. These are all things that are precious and hard to come by. But in the end, until she is willing to understand why she is doing this and admit to herself the underlying causes and actually WORK ON those things, nothing will change here, and you're only enabling her destructive habits. Since she's in the kind of situation where it seems she may never actually look at herself in the mirror and say "okay. I'm gay. And that's okay!" this situation is never even going to begin to change. Even if she were to do that, she would then need to do a ton of introspection and soul searching, and actually make real, concrete changes in her life. Not saying it's not possible (I did it) but it certainly is incredibly hard, and it has to start with a very painful, realistic look at yourself and desire to understand why you're doing this. Most people simply can't or won't do it. Maybe try to talk to her, but be prepared for denial, defensiveness, hurt, and anger. That's all I would have felt before I actually grew up and evolved.
Also, just a side note, this guy that I was doing this to? We didn't speak for a couple years, and then we became friends again, had a looong, honest talk, and we now actually have a healthy friendship. It IS possible to reconstruct a relationship after events like this, but only if she's willing to evolve, and it sounds like she is not. I'm sorry you're in this situation because as I said in the beginning, I have been on the other side of this too, and there are few things more painful than having your heart's desire dangled in front of you and knowing, deep down, that it is not going to happen and shouldn't happen, no matter how much you love her, how much you connect. Some actions can never be taken back. She's betrayed you in more ways than one, and no matter how sweet she is or how much she changes, that betrayal happened and it can never be taken back. I may be reading into all of your words too much, but it seems to me that you already know these things and you know how this is going to end, but you love her and are trying to convince yourself things could magically get better. Unless you can turn back time and control the minds and actions of others, you're going to have to accept the things that have happened and accept the reality of who she is and what she has been doing to you for YEARS. No person who loves you would do this to you. I had to learn that the hard way.
Whatever happens from here out, I truly only wish for the best for you. This is a painful and difficult place to be in. It's like having a thorn in your heart that constantly aches and poisons you, but you don't want to remove it because then you'll have a big hole in your heart. Believe me when I tell you that the hole will heal, and someday you'll look back and wonder why you kept the thorn in so very, very long. Hang in there. My inbox is always open if I can ever help you. <3