starved mare rescue

my mum and I are trying to save this starved mare, the photo shown does not do her justice (please message me for further pictures) apart from her being starved and in such bad living conditions she is also suffering with a mouth abscess, ever grown teeth (probably never seen a dentist) and also has eye infections in both eyes. the owner is wanting 400 for her and won't budge  on the price considering what of a bad state she is in. with this and the costs of the vet and on going treatment she will need plus specific grain etc... this is why we are requesting the target we have set even though it will end up costing far more in the future, but we just need to get her out of where she is before the owner sells her i.e. to slaughter.  as the situation she is in now I'm worried she will not make it much longer in the state she is in and defiantly wont make it through winter. this is an urgent appeal, so any donation no matter how big or small will help and be very much appreciated. please feel free to share as we need all the help we can get to rescue this mare.