The 30 minute wait is obsolete. Now she appears as soon as you capture the ghost. Once she appears you must talk to any of the boys until you get her name. After that you will find her in the past.
Viewing post in All Possible Animations (Contains Spoilers)
for some reason, i have the same problem and i still cannot figure out how do to it. do you need to do this the 1e time or event after that its fine? cause she never seem to spawn after i capture the ghost after i leave and comeback again. also event following the guideline, and set the good symbol, she never move from the bottom floor and seem stuck there.