Hrm, snakes have really good memory (which was really surprising to my parents)--they just need to get out once and that's the route they will try first until that fails. I would stay with her for a day/night/whenever she gets active (or set up a camera if you don't have that kind of patience) and figure out exactly HOW she's getting out. She might be doing something you would have never imagined her to do.

The solution might be simple, then again it might not be.

I think your set-up is amazing, if I had that kind of dough to get this style (and didn't move around from school to home so much) I totally would. But it seems to me she has some sort of leverage against it to pop it open, or can bend a portion of it to get out.

My biggest fear would be that you only semi-fix the problem and she gets stuck trying the same way she got out before so I'd watch her until I find out how she's doing it.

(I once sat up until 4 in the morning trying to figure out how my female was escaping

it was not a good day after.

=_=;;;

but on the plus side ever since I fixed it she hasn't escaped again.)