Yes, a Butterfly Bush can be moved. It's best to do it now while it is dormant. You can also do it once it leafs out, but it will pout (wilt) for about 2 weeks afterward. As long as you keep it well watered after it's transplant and try to take as many roots as you can with it, it should do just fine.

I moved mine a few weeks ago, just after I pruned it down to about 12". Like you, I planted mine last year. It had an amazing root system already, and some very long, thick roots just had to be cut. So far, it seems to be fine. No wilting even! It was leafed out when I moved it, but barely. Dig a nice big hole for it before you move it so you can replant it before it knows anything happpened. Good luck.