Oh Helen, I've just logged in and read the awful news. So very sorry for you all. Love and hugs to Katie, bless her.
May I just say that if you 'milk' her she will just keep making more. She has to be 'left' to dry up, perhaps your vet has something to help in this respect.
Also (my personal experience) please do NOT remove the foal. Mares need to keep their foals for as long as it takes for them to accept the death. This may take a few days or more than several, often more than a week. When she's feeling a bit stronger let her go out into her paddock - or wherever she is normally - and carry the foal out too. We have carried foals in and out for over a week, then suddenly the mare will leave the foal and go off to graze. The next day we leave the foal in the stable and put just the mare out, and if she goes off calmly and doesnt return to the gate during the day, calling for the foal, then we will remove it from the stable before the mare returns for the night. If the mare is then ok for the night, the foal is then not returned to her.
It can be a long process, but you end up with an unstressed mare by doing things as nature intended. Other horsey friends or companions can often help to speed up the process.
Do hope Katie will continue to recover speedily. Think of your beloved dog waiting at Rainbow Bridge - waiting to greet and make a friend of a new little foal.