You're on your right to take your own path.
Now, let's talk about this "relationship". Seems to me like she doesn't want to lose your support, but she's not willing to give you your rightful place. That is, she wants the rights but she doesn't like the duties.
If she loves you so much as she claims, then she has to "understand your situation" and accept it. Is for your sanity and your well being.
Also, I would say that the so called love that you talk about here is sort of a platonic thing, since you haven't had the time to really know her deeply and live with her. When we're "in love", we tend to discard the bad and highlight the good qualities of the object of our love, so I would suggest that you keep your decision strong and let her deal with her ex until she defines what she wants.
You can even tell her to come here and ask for help
Keep strong, you deserve better!
Of course, dating her for those couple of weeks was tough. She already knew in her head that she wasn't going to be with me for very long, but she became controlling and pointed out various things around my house that I needed to change. "Don't use this kind of shampoo!", "Buy a shower curtain to go with the liner!", and "You don't want to use hair gel!" were among her complaints when she stayed over. Some of the things she said actually got to me, and I found myself throwing out an expensive bottle of shampoo and hair gel that I had hardly used because I was worried I had to get something more "natural".
While we dated, one of her major complaints is that she had a lot of things she needed to work on with herself, and she wasn't ready to jump into anything serious. When we broke up, it was because she said she wasn't in the right state of mind to be with someone, and needed to work on herself. A couple of months later I ask her to hang out as friends, and she reveals that she is seeing someone. Well, that was fast! Meanwhile, I am still single.
The way you gotta look at it is, you got to sleep with this woman. You got something out of it, so all of it wasn't for absolutely nothing. If you had devoted all of this time and care to this woman and had gotten nothing in return still? Well, you might still be following her around like a lost puppy, enamored with her - meanwhile you're not getting anything out of it, and she gets to feel loved from all sorts of people. But you got to have your way with her for a bit, so that's your reward for putting up with her bullshit.
I wouldn't even bother trying to figure out what's going on with her - why she is back with her ex, why she led you on and slept with you, whether she is lying or hiding something or whatever. Just be happy you got to sleep with her. Now I guess look for the next girl you can sleep with, and who knows, maybe she will actually be into you?
Can you see that she is "all-self" about this? This girl wants the best of all worlds.
She used you as a re-bound man and wants to keep you in that slot - in case it happens again, which it probably will, since her relationship is flawed with him AND you.
She keeps her finger on you, so that you will be "there" when she needs you. She needs a fallback man.
So - it's up to YOU to get control of this relationship, which is to say END IT COMPLETELY. Block ALL kinds of contact with her. Don't answer any of her efforts to engage you in any conversation or bargaining about your relationship.
Of course, this will take courage and determination from you. If you want to get out of this pain, then decide that you will no longer be treated this way and deserve better.
Discussion closed - why not create your own thread?