Thank you for the added information. It helps a lot in being of help with this issue.
First, let me say I can imagine how frustrating and distressing this situation must be for you. I'm with you on her being young, stressed, and so needing to withdraw. And that her sister did this before her gives it a precedent as well. I don't rule out negative reactions: she may say it's bad, but that her sister did it can give doing this some legitimacy. So, stress can be a big factor.
Ultimately, we don't know. But she sounds like a really fine young lady and you clearly want to try to make this work. So, we're going to have to come up with something a bit subtle and a bit out of the box here. Because she's not going to be swayed by the usual pleas, logic, appeals to loyalty, etc. She's trying to sort things out.
Therefore, I have an idea, but it is out of the box. She needs independence right now. Granted, treat it as a given and don't fight it. But you need communication. Because if you two don't stay in communication, then she will drift apart and so will you.
Communication is the muscular system of love. And love is the circulatory system. Let me repeat that because it's so important: it's not sex; it's not beauty or looking good; it's not being smart or clever. Communication between the two people is the love muscle; it's the muscular system of love. That's where my idea comes in. To give her that space and independence but to keep the love system flowing through communication.
I want you to print out this part of my answer and take it and her to a Starbucks or other quiet place and discuss it and see if she'll commit to this program. You're going to start with a book. You'll get 2 copies, one for each of you. Every couple of nights or so you're both going to read a few pages or a chapter and do the exercise there if there is one in those pages. Once a week you will get together, either at home or at the Starbucks and talk about what you read. What you think of it, what it inspired in you. Make notes in the margins. And each one talk about the subject of the pages and what you think. That's your date.
The book is the Seven Principles for Making Marriage Work. You can get it cheaply online or see if you can get it locally to save time. Don't get put off by it being about marriage. It is about relationships at its core. I know it's taking a chance, but you are looking for something to keep you two connected so that you can get through this anxiety period together and become close enough to move in like you were going to do.
Because this is the secret: the magic is not in the book. The exercises and Gottman's insights will be very useful and important for the two of you. But the magic is in the act of working together! That's the magic ingredient we're looking for.
Okay, I wish you the very best!
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