My best advice assuming that temps and feeding are ok and that she has had some time to adjust to a new home would be the following

-Try not approaching from over head. Most threats for a little snakie are going to come from over head as it is. A huge monster coming from overhead is going to be a threat at first for them
-Keep handling. When s/he bites, keep working with him/her. Its much easier to work on taming a young boa rather than a 6-7' boa that you may have in 4+ years.
-Get on a regular feeding schedule. I have heard lots about boas being a bit more nippy when they are hungry. I thought it was BS and then I tried feeding my young hog more often and she has calmed down considerably, not even handling every week in some cases.

Thats all I can say until we know a bit more about what kind of boa you have and your setup