Great question, so glad you asked.
It's not a matter of what she has been exposed to (kudos on not letting her watch tv! You are doing her a tremendous favor - read Marie Winn's The Plug-In Drug for more motivation and reasons not to be a tv family).
It's biological - babies and young children have, throughout our evolutionary history, stayed very close to their parents at all times, or else were easy targets for predators. This is probably why they tend to get upset easily if left to play by themselves for longer than a few minutes at a time, even during the day time. As someone said (I don't remember the source): "those monsters in the closet and under the bed are real. They're just extinct."
Don't let her cry it out. Think of how traumatic it would be to be left alone in a dark room with shadows everywhere seeming so alive and threatening - and on top of that, to feel that she can't count on her parents to save her from her terror. Believe me, it is sheer terror for a tiny child to believe there are monsters all around, and her tears are there for a real reason. She's not manipulating you.
I was going to suggest that you use another night light. But you might need a few or maybe even a low-level lamp would do it, even though it might seem very bright.
It probably won't end there, though. I think a really good idea would be to agree with your husband to let her sleep with the two of you for a few nights, to give her body a chance to taper down on the adrenaline response that she has developed to the night-time situation (think of how you feel after a scary movie - sometimes everything can scare you as you walk through your house after watching one; this is an adrenaline response). It really is a physical response at this point. Tell her it's only for a few nights till she is more ready to go back to her room, and during those few days and nights, figure out some good night lighting, and show it to her, and show her, during daylight hours, all those things that scare her. Show her that they're not scary. At night, visit them together, while she is secure in your arms, before you take her to your bed. Ask her if she still finds them scary. Play with them, and show the difference between how they look in the light and the dark, and explain that shadows can look scary, but if she starts to feel scared, to remind herself that they're just the same as always, and look away and think about happy things. If these tactics don't work, just put those things out of sight if possible, or, if not, make sure the lights you put in shine on them in a way that doesn't create a dramatic shadow. A light from overhead, or higher up on a dresser, might work better than night lights near the floor, because the shadows will look more familiar to her.
And whatever you do, don't force her to cry it out! In terms of her emotional and psychological health, she really needs your help on this, not for you to turn your back on her through such a trauma (anything that leads to prolonged crying means they need you, so, actually, never make a baby cry it out).
L.