D.P.
M.,
It might be her eye teeth which I remember being VERY bad. If it IS teething, have you tried Hyland's Teething Tablets? They are all natural and supposed to be great. Can you give her infant Tylenol to help with the pain? Wet, fold and freeze in a ziplock little washcloths and give them to her to chew on.
Kids often get congested when they are teething and it may be interfering with her sleep. Have you tried elevating the head of her crib and running cool mist in her room?
If she's in pain, I, personally would not let her just cry. She needs to be comforted. There is a difference between a kid who WILL NOT go to sleep and a kid who CAN NOT go to sleep because he/she is in pain or discomfort. There have been LOTS of posts on this site regarding teething and if I were you, I'd take a look at all of them because there are lots of great ideas!
Hang in there--this won't last forever--it just seems like it :) Good luck.