I agree to turn off the baby monitor at night--and don't worry, you'll hear her if she needs you (I can sleep through a thunderstorm, but if, across the house, one of my kids whimpers from a bad dream, I'm suddenly wide awake, lol).
Other than that, I'm with Kelly W. on this one--go with your heart. I have three children, and I never was able to let them "cry it out." It made ME way too anxious and just didn't feel right to me. (My instinct tells me if my baby cries, it's because he needs something!) Personally, I'd much rather go in the room and rub the baby's tummy for a few minutes than listen to him scream for a half hour or more. (For the record, they all still learned how to soothe themselves just fine.) ;-)
You might try using other methods to soothe her, though--try to avoid picking her up if possible so that she doesn't get used to the movement. Rub her tummy or her back, or stroke her head instead.
As someone else mentioned, you could also try soft "white noise" to help block out night-time sounds that might be waking her.
Also, does she sleep much during the day? It may help to shorten her daytime naps a little. Make sure her room is comfortably cool (not too cold, not too warm), and that it's dark enough; too much light could be throwing her "body clock" off a bit.
Speaking of light, I don't think using a night-light will help unless she is afraid of the dark; it's more likely to disturb her sleep than to soothe her at this age.
Lastly, if this seems to be a fairly recent change, she may be teething or just going through a phase. If nothing else, try to remember that this, too shall pass! :-)