It's not random. Every time you catch the ghost they appear near first floor stairs provided you are not in same room and didn't get her name. If you learn her name in a dialogue it begins her quest.
why i can't see her in the past , i wait until that 2 guys finished and back to the portal go back in the past and still can't see her (sorry i not good at english)
Look you should talk to her and give her mirror then talk to her until she wont say "go away" but if she dosent apear in past then try close game and launch again and of course you need get first part of her quest
