If you're not willing to make her uncomfortable and challenge her to develop confidence, I don't think there's much you can do.
If you want to build a resilient child, you have to look down the road and endure some short term discomfort. And if you value your marriage, you will not have a child in the marital bed or be sleeping in the child's bed instead of yours. This is where, long term, she is learning what marriage (or partnership means). Is that what you want?
So how was it that she cried from 9 PM to 2 AM? Did you leave her there? Did you go in and talk to her? Did you go in briefly and be firm, then leave? Did you do it for only one night? And here's the hard questions: Is this about making YOU more comfortable, or her? And because it didn't work a year ago, you gave in, right?
It sounds like you're trying to use logic with her (night light, helping her understand the number of feet between her room and yours, etc.), but this is not a question of logic. It's a question of emotions, of you being a human security blanket, and of you both being more attached than is working for you. While you feel like you are reassuring her, in the long run, you are handicapping her.
So, I'd suggest that you do what many people do with 6 and 9 month olds, except that you can prep her with a certain amount of planning and some discussions of the "big girl" privileges she expects (whatever it is - bike riding, using the computer, going to a friend's house, watching a certain movie....) and contrasting that with her lack of maturity/confidence when it comes to sleeping. Beyond that, you do what we do with young kids: You put them to bed, you don't give in to whining and emotional blackmail, and you go back in 20 or 30 minutes, pat the back (do not lie down, do not have a conversation, just say "You're fine. Time for sleep") and then you leave. And you (or better, your husband) should go back in maybe 45-60 minutes later and do exactly the same thing. Exactly. Do not linger, be matter-of-fact. Both parents use exactly the same language and technique - whatever you choose, agree on it and do it to the letter. If he can't quiet her down, he doesn't send you in though!
The next day, if she has kept you up a fair amount, you present the facts: you are sleep deprived and exhausted, and she is sleep deprived. You're too tired to drive, and she's not sufficiently rested to do XYZ. No blame, no guilt - just facts. Yes, play it up a bit, but don't be overly theatrical about it. Sort of like "no dinner, no dessert, no argument." I'd also consider a quiet time for her mid-afternoon since "you had a rough night and maybe a nap would help." If that doest work, you can certainly give her time in her room while YOU take a nap, alone, in your own room because you are exhausted. You have to take away what she wants - which is control over you and togetherness with you. The point is, crying and whimpering and whining and screaming at night cannot be a successful behavior for her, and she cannot get a payoff for it. Personally, I would choose a 3 day period including a weekend and just decide you'll be miserable every few hours if necessary, and then you will be done.