I feel it's a bug. To be honest I just went into the code and changed the condition within if statement. I remember that there was the flag that should be 'true' if Prism is with you, but since she never appeared it was always false for me... so I set it to be always true and automatically moved to the next scene.Did you ever figure this out? I'm having this same issue not and I have no button to summon her
A bit messy, but it worked, though I cannot be sure if this kind of tinkering haven't skipped some other flag, that will bite me in the ass later on