I got filled in on a sort of interesting exchange that apparently went down between Cynthia and Caitlin at some point during the past year, probably before Caitlin put away the pocket-watch and when she was still floating around in her little ocean of depression.
Cynthia was really concerned about her during that time, and rightfully so! One day during their little movie nights where they lazed around and just sort of enjoyed each others' company, Cynthia brought up that Caitlin had been acting differently and asked if everything was okay. She probably just got a small, meek affirmation in response and then this sort of happened:
"I miss him! I do not know where he is and I miss him. I thought we would be together, but we aren't and I miss him."
"Caitlin... It's been months--"
"I know how long it's been, Cynthia, please do not feel the need to remind me--"
"Are you ever going to stop waiting?" and man that just sort of hit like a slap to the face, because until then I'm not sure Caitlin had ever stopped to consider the idea that she could do that, that she could really move on. And she was quiet for a long time but Cynthia didn't say anything else so eventually she answered
"I do not think I can."
"Of course you can. You're miserable--no, don't give me that look--you need to move on with your life. You're too young to be this sad over one man."
"He is my whole world."
And oh man Cynthia was furious. Like... the kind of mad that you see your mother get when you know you've really screwed up, the cold kind of mad that makes her seem to freeze and turn to look you dead in the eyes and it's frightening, that's exactly how Cynthia reacted. She got really still and really quiet and turned really slowly and I can't remember her being quite so angry before.
"Don't ever say that again, about anyone. Anyone." and Caitlin probably started trying to protest, but Cynthia just stopped her and repeated it.
Caitlin just sort of nodded in agreement that she didn't really mean and they were tense and angry for the rest of the movie until Caitlin left to go back to the league all in a huff, like the sort of upset where her powers start creeping back out of her control and she stormed straight to her room and wouldn't come out for a long time until she calmed down.
I think this is what was really the turning point in her progression to being ready to let go. She was angry about it for a while, but the more she thought... the more she started to understand that Cynthia was right. It was probably the first time she realized how much she'd been letting her feelings revolve around Darach and it was something of a wake-up call.
