As long as the Jilly has someone with her I would say it's ok to be outside for a while. Remember though that bunnies love to dig.....they may get in to mischief by digging up your flower garden (not that that would happen in winter)... However, the thing that concerns me most is that they will also dig under fences and can get out and lost.

Ideally your fencing should be sunk 12 inches beneath ground level. Since that's not practical you'll have to keep an eye out for any signs that she is digging by the fence.....ESPECAILLY when spring, summer and fall comes and Jilly can be out for longer periods of time. I would hate for you to lose her that way.