you sound so frustrated and depressed. you must be exhausted. you didnt mention how old you daughter is or how long she has been sleeping so badly for.
all i can say is that i agree with what william sears says in his book 'if it isnt working change it' and things dont seem to be working for you.
recently i had to rebuild my cot after 3 years of cosleeping happpily with my first so to put my second son in. i felt really weird about the whole thing but he was waking up between 2 and 3am every night and staying awake till 6 or 7am and i was a wreck - physically and emotionally. i feed him to sleep put him in it and he does the weirdest thing - he sleeps all night without nursing or anything.
i am amazed oliver night nursed till he was 2years and 8 months oscar is only 9 months old. but what the heck - it works.
maybe you need a change of routine - a change of bed or bedroom, we have had different beds in different rooms and all sorts of srrangements and try to do whatever works best at the time.
you are a fantastic and devoted mother and you should give yourself a pat on the back but also try and work out something new to help you feel better. i find sometimes just having a plan is enough to make a difference to how i feel even if the plan doesnt work out that well.