Our son slept through the night from 2 months to 6 months old. After that, he was up during the night multiple times for a very, very long time. I remember during that time when he was sleeping through the night, our doctor told us not to get too excited because that would change... and she was so right. By the time he was 8 months old, I was so exhausted that we started using the Ferber method, which seemed to work in terms of getting him to fall asleep without being rocked, temporarily at least (every time he got sick or we went out of town... we would have to start the process all over again...) but letting him cry during the night or for naps NEVER worked for us. My husband also was getting up at 5:30am at the time for work and there was no sense in none of us getting any sleep with baby up crying histerically all night. So I would get up and rock him back to sleep... This went on for a long, long time.
We eventually got rid of the rocking chair so that that was no longer an option. And once we put him in a big boy bed at 16 months old, I would just go in and hang out on the floor next to his bed when he would wake up.
Teething could certainly be the issue. Have you tried giving her motrin or tylenol before bed? If it is teething, that will certainly help. Make sure you get the proper dosage from your doctor first though.
We found that the book "the no cry sleep solution" had lots of helpful ideas and it really ended up getting us through that tough period. We had a great sleep routine to begin with, but this book really helped us follow through from a lot of different angles... I'd recommend picking up a copy...