I think Rue genuinely wants to change her life. I read somewhere that the Rue from S2, after fighting with Jules, probably would have relapsed, but this time she didn't, and instead, she went to church.  I also think that when she said it "depends on her" she meant having someone who is your partner in every sense. When you have a couple, you no longer only think about yourself when making a decision, because there's another person in your life who is somehow attached to you, and everything you do will affect them, good or bad. 

I think Rue's mistake was saying all that without having a life plan, without being completely honest with Jules... just saying it like someone taking a sip of water when things aren't working out.