@Raspberrysins
The exercise is evolutionary. You won’t be able to stop the urge until your dd has regained quite a bit of weight. She sounds rather emaciated. The urge stems back to when we were hunter / gatherers and food was scarce. Some people would get super energy and walk for miles in search of food and / or a better place to live with more food for the rest of the group. That’s why anorexics have oodles of energy, until they suddenly don’t.
As for how to handle it, my dd hasn’t had these urges in a major way. I think a lot of this is because I have managed most of the time to have her eating enough or turned her around from relapse. If it is medically safe to do so, it seems to work best to offer exercise in a limited and controlled way.
Dd for example had to stop all exercise for a while, but was allowed to meander around with her friends, but not too far. I was giving her lots of lifts to and from the park 10 mins down the road to reduce her energy expenditure. After she put on some weight, I allowed her to dance again, but 6 months later she subsequently had to stop following a relapse. I offered the gym instead, as she really needed a form of exercise. She was initially allowed twice a week and this came with 3 PT sessions. I ensured the PT had knowledge of ED and would train her based on needing to be conservative with exercise.
As for your dd, she’s more at the meandering around stage. ED services used to say no exercise. Now some are coming round to the idea of a little exercise to keep morale up for those, always on the go.
So presuming it’s medically safe and your dd is eating regularly, even if not yet quite up to the full amount, going on the short walk she did the other day may reduce the movement at home. Therefore she may actually be using a similar amount of energy with the walk.
You could talk to your dd about this. And use it as a bargaining chip to add one thing in, telling her she can go for that walk that day, or indeed every day. Make it something worthwhile if you do. Eg Is she eating enough protein for example? It’s actually really hard to regrow new muscle, which is why I’m highlighting it. For protein, you could add in some cheese to be eaten before she goes, eg 2 full fat babybel. If she needs more fruit / veg, something like an orange, a banana or some mango (rather than watermelon, which is diet food) plus a babybel etc. Adding in the cheese reduces the GI and stops the sugar spikes. Or if she just needs to eat in general, add a flapjack etc.
And this is a good way to increase intake. Carrot and stick. It works equally well for anything they really want to do.