I think at this point everything we are discussing is just open speculation. There is no confirmation that she weighs as much as 63 stone, or 56 stone, depending on which report you read, only that they had to take her home apart to get her out, so all we can conclude is that she was pretty dangerously ill and too big to move herself. If either of those figures are accurate, then she is either nearly 800 or nearly 900lb in weight. I cant imagine being in that situation and feeling anything other than entirely hopeless and out of control of your own life. Yes, she could theoretically have said "no" to the food she was given, but at that point, she must have pretty much not had anything in the way of a will to live anyway - she would have been merely existing rather than doing anything remotely resembling living.
What we, as a society, should be asking ourselves is WHY this has been allowed to happen. At 15, she became the nations freak-show of choice for a short period of time - enough to make anyone reclusive and want to hide away from the world. If I was her Mother, I would have been banging the GPs door down BEGGING him to do something to get her out of the house and to some medical help. When she was capable, she was begging for the help herself - but she never quite made it to where she wanted to be, so gave up. I do actually think, had she been given the chance to get to where she wanted to be, things could be very different now, she would have experienced a feeling of pride in herself, a sense of achievement, and that she had cracked it. She never got that. Too easy to slide back into old ways when you feel like a failure anyway.