Poor you! There's very little worse than a hungry baby won't eat, must be terribly difficult for you right now. My DS had thrush AND reflux so hopefully I can be of help.
Thrush -you can tell if they have this because their mouth will have little white dots in it that don'trub away when you smooth your finger over (milk residue would). Don't rub too hard if this is the case because the skin underneath is red raw andwould be painful. If there are white dots get your HV round again and get some meds. Also with thrush you need to sterilise with miltons or something like as a steam/microwave steriliser isn't good enough. Also make sure you wash your hands before and after each feed religiously as it can be passed between you.
Reflux - we could tell DS had reflux partly because he cried after his feeds and wouldn't eat properly, but also because he would throw most of it back up - reflux babies don't always throw up though, it can just be the 'heartburn' element of it. If DD is showing a preference for sleeping on an angle she might have learned it's more comfortable like that - try propping her basket/cot up on books/bricks rather than letting her sleep in the bouncy chair though as it's better for posture. Sickness with reflux follows a pattern too -they have one bout immediately after a feed and another bout 1 1/2 - 2 hrs after which is when the tummy pushes the milk into the intestine except with reflux it goes the wrong way.
2 schools of thought here. 1) feed them little and often - this is because after a short time the milk starts coming back with acid and can be painful but by feeding them only a bit they should keep most of it down. 2) feed them as much as possible and give them about 4 hrs between feeds, this works on the principle that no matter ow much/often you feed them it will hurt and they'll be sick so you might as well keep discomfort to a minimum.
Thankfully they do grow out of reflux but it's distressing for mum and dad too because they know baby's in pain. An effective treatment to try would be infant gaviscon (available from chemist or on prescription), this makes the milk thicken once it goes down so it doesn't come back as easily. If you try this and it works go to your GP and ask for a prescription of Enfamil milk which already has the thickening agent mixed in - it costs about the same for the GP to prescribe as gaviscon so there's no reason s/he should be against it. The other advantage of this is that gaviscon contains sodium as does formula so baby's getting a double dose, using enfamil cuts that out.
We ended up using the controversial gina ford routines for feeding but found they worked really well - this is the 'as much as poss 4hrs apart' method.
Newborns can sometimes find feeding upsetting because they have a blocked nose - have you listened to her breathing while she's feeding?
If there is projectile vomiting involved ask your GP about 'pyloric stenosis' or google it as sometimes discomfort following feeding can be more serious.
Sorry for the essay - just wanted to be of help as we were so lost with DS and it could have been much easier if I'd known about MN then!