Does she have wind?
When my DS was born he was breastfeed at the start,and alot of trouble was he wasn't getting his wind up,which meant he was crying all the time,and i didn't have enough milk.
i changed her onto formula at 4 months as she was all over the shop with feeding,was doing it every 2 hours.Once on the formula after about 5 days finally got him to every 4 hours,but it took time.
Have you tried elevatian her cot up a bit to see if that helps he sleep?
When we arrived from Australia to Europe he was 6 weeks and didn't sleep for the first 2 days with jet lag,then we had to sleep him in a rocker for the next 2 nights.We had to make his mattress more softer and now he sleeps all sleeps in his cot.
Maybe talk her for a walk to try and stretch the feeds out?We use to put our DS outside all rugged up in 4-5degrees as he would only sleep in the fresh air.Alot warmer now,so maybe some walks might help you stretch the feeds out more?
Hope some of this might help you...
There is light at the end of the tunnel,I no it doesn't feel like it but you get there eventually,it took me 4 months but now he is really good.