I remember around this age my ds did the same, it is so hard!
if you can try and get her to sleep by any means it could then break the cycle, better day sleeps means better sleep at night, its hard to understand but its true, (even for ds now) you'd think if there that tired they would sleep all night!! but for some reason it dosen't work that way.
maybe try a walk in the pram? are you wrapping her? because that could help, what about a dummy? or even a sleep in bed with you?
it is such a difficult time - you are doing a wonderful job and believe me it does get better!! and soon she'll get more efficent at feeding so feeds will get shorter and you'll have more down time in between feeds.
hope that helps?! all the best!