endgame bug (spoilers)

[vio]

ok so I fought Jack in the guild hall, killed him and my sister tells me I can throw the sword into the vortex or kill her with it. well, she's half right. or at least, I'm assuming I can kill her with it, but I'm saving that option for my evil character. however there is no option to throw the sword into the vortex. I've tried standing around it at every angle, the f1-3 slots stay empty except when I target my sister when I have the option to do an arm pump or a pose (f1 remains empty)
talking to her does nothing
equipping a different weapon makes no difference
drawing the sword doesn't help either

[vio]

reloaded and did it again and this time it worked fine, popped up a question as soon as I approached the vortex this time. bit of an annoying glitch though