BBV - hey bro, glad to hear your lady at least talked to you about some of this over the weekend. Hopefully you two were able to communicate enough that she'll realize you're not forcing anything on her; that you do care about her and that over the past weeks or months you've felt like she no longer gave a rat's ass about you and was only concerned with showing off her goods (though in a more tactful manner).
You'd think that her buying conservative clothes for work, tossing out some of the skimpy shit you hate, yet buying new skimpy stuff to wear for you at home would tell you that she's sersiously thinking about what you've been trying to tell her. At least I know you're hoping & praying that's her reason. I see where your skepticism, or worry, on that issue still remains. Has she told you that she understands where you're coming from and knows that you have the best of intentions, even if she's viewed it as "you have no right..."?
Your cancer analogy isn't really the best. I understand what you're trying to say, but someone with cancer is sick and it's difficult to heal. What you're going through is watching someone you love kill themself and your relationship. Regardless, it's still painful to watch and know there's not much, if anything, that you can do to stop it. I feel like you've done all you can or anyone would expect you to...the ball is in her court now. She has to make a choice. If you "loose" her, it's because she didn't know what she had...not because you didn't do or give enough.
Just try to keep it all in perspective while the road is still rocky. Hopefully things will continue to improve with her, but don't let yourself be walked over. If the problems persist and she continues to place this wall between the two of you, walk away. No person, regardless of how much you love them, is worth your misery...especially if they're the cause of it (this excludes a person's children).
Good luck bro.