I can't see any suspicious script blocks but the issue is definitely Sandrah's script.
I strongly suspect that either script blocks that are executed while the inventory screen is open are not displayed or, more likely, the issue is caused by blocks that don't return true. Maybe just a loop or a whole bunch of checks al at once. Those blocks would not be displayed by that mod, right?
In any case, as before; if I remove her override script the lag is completely gone, with script active everything but her book lags as hell.
Look for this section of blocks in the script and delete it - see if it helps (of course the strgrefs will be others)