Hiya,
Does she fall asleep by herself during the day/in the evening in her basket? I found that as soon as my son learned how to go to sleep by himself he settled better and for longer. Also you may need to let her to cry it out although co-sleeping is fine in the short term it is probably not something you want to go on too long.
Might be worth making sure she's not sleeping too much during the day or skipping feeds as she's asleep...
I did the Gina Ford routine with my first born and they really worked, they're not for everyone butnyou can follow to the letter or use it as a rough guide but the principals make sense...by 4 weeks my son was feeding 7,11,3,7 and sleeping 2-4 hours between the feeds. He slept through the night from 11-7 from 3 mths which was a godsend!
Good luck
Gem