It sounds like the previous counselling did not fully get to the root of the problem, or successfully resolve it. Some sensitive children can be very affected by events that seem remote to us. This could have been triggered by something like hearing that a mother was killed in a terrorist attack in London, for example (just to give one possible explanation. Of course it could be something quite different).
The problem is, sometimes, that although the chances of something happening to you on each occasion you leave are very very low, the risk is not zero. This can be very hard to handle for some people - the fact that there is any chance at all - however remote - of anything happening can be enough to make it extremely hard for them to let go of the anxiety.
I would suggest further therapy, with an experienced children's psychotherapist (rather than a counsellor -look for somebody UKCP accredited) to tease out exactly what it is that is bothering her. Nameless fears cannot be resolved, she will need help to bring them to consciousness, so she can deal with them properly. It could be that at the moment her mind is pushing the detail of her fears out of consciousness, in a misguided attempt to protect her/avoid the anxiety. Unfortunately, this is an unproductive strategy.
I can imagine this is very tough for you, and I realise how frustrating it can be. If you can possibly avoid reacting with anger, however, it would be helpful, as it will make things worse if she feels you don't understand, and are punishing her for being anxious. I know it is very hard, though. I would not, however, allow her to stop you from going out, as this will just entrench the anxiety further. She needs to see you going out repeatedly, and coming back fine.
Hope you get some movement on this soon.