I'm pretty sure that's normal. Mine did it when I first got him, and he still does it every so often, especially right after he eats.
When you think about it, ground boas are nocternal ambush hunters, so they're normally not active in the day time and the way they hunt is to sit still and wait for something tasty to walk by. Between these two factors, I don't think it is unnatural for them to it in their hide with their head poking out just in case a rat shows up.
Although they do many times get active after a while, I don't think it's necessarily a sign that something's wrong for them to sit around most of the time. She may well start moving around more when she's been living there for a while longer, though.