Hi Mandy
I know this is all very stressful - but do not ignore a letter that has no name and no reference on it. Pick up the phone and ask them to clarify that the letter is genuine and meant for you sister and ask about the length of the award. There is nothing to stop you from doing this. I've heard of quite a few letters that have no end date, but not without a name on it.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems