Haste is busy gathering a vantage point that she'll both be able to look over Bast and Jessie, and protect both of them should the fire come into the building.  Hopefully she'll just be able to run and throw herself in front of any blast coming at them.  Of course, being unaware as to the type of spell that Bast is casting she doesn't know to offer up carrying the other woman into the main building.  Not that she could leave Jessie here of course, but she's sure they could figure out something.