If you are onsite, call guest relations every day, even twice a day to see where she might be. If that doesn't work, ask when you enter the park for the day. Keep asking until you find her.
Several years ago, on our first visit, my daughter had her heart set on meeting Cruella DeVille, another elusive character. I asked every day and no one knew where to find her. Finally on our second to last day, someone said she "might" make an appearance that afternoon at MGM. We weren't planning on MGM again, but over there we trekked. Asked again and were told, she might be out between 2 and 3 that afternoon by the Chinese Theatre. Went back there at that time and the CMs said, no, she wasn't scheduled to be there. Oh, no! But we related our story, he left and came back and whispered that she would be out shortly for a brief visit! We had her almost to ourselves and she is a delightful character! Scared my son to death LOL but it was all in fun.
HTH