I feel more sorry for your mum that you aren't supporting her! I don't mean that in a bad way against you - but, honestly, doing a VLCD really isn't that bad.
if she is feeling run down and tired then it is not for her. At least with Atkins she can get some food into herself and might feel a bit better.
As an ex-VLCDer, I would have to disagree with this statement. What you mum needs from you is your support to get through these hard first few days.
I did Lighter Life, which is basically the same as Cambridge... and the first few days are horrid. As with Atkins, the first challenge is getting into ketosis - on a VLCD this tends to happen quickly, usually 3-4 days or so.
I know I may sound a bit of a weirdo hailing the brilliance of a VLCD when I am over here doing Atkins, but bear in mind I am not here because VLCDs are 'bad for you', 'don't work' or anything negative. I did food replacement for 5 months, lost just over 5 stone and changed my life forever.
In the end I felt so amazing I gave up (doh!) before I reached goal, and I have now decided to get the last few off. This time around I am much smaller and therefore don't thing I require the extremity of a VLCD - plus I now want to learn how to eat as a 'way of eating', not a weight loss tool.
If I had my time again, and I had a lot to lose - I wouldn't do anything differently. I felt the best I've ever felt, full of energy and bursting with life - shiny hair, strong nails, glowing skin... and those in my group, on the LL side of minimins, said the same. The nutrients you get from the food packs are so vitamin dense that you actually end up 'better' than the majority of people that don't balance their meals carefully enough.
Rather than pitying your "poor mum", you should be proud of her and excited for the journey she has just embarked on.
Yes Atkins is BRILLIANT, but it's not the be all and end all. Cambridge works on the same principles (using fat for fuel), but it is usually faster and the relief of putting food to one side for a while, and being able to just concentrate on 'being' is so freeing for many of us who have been haunted by food for years and years.
Anyway - that's all. Good on your mum for taking this step to get herself healthy. Atkins may be the best step for her to maintain her new found sexy figure towards the end - but live and let live.