Somehow, something doesn’t seem right with this. It just seems to me that if its God calling her away from one she has loved, it would not not such an either/or thing where she would have to reject you in order to embrace God. It seems like she woudl be able to show she was glad to see you, and even if she made up her mind to cool off and redirect your romance, she could do it more lovingly and patiently. It seems like she would be capable of imparting her thoughts to you in such a way you would understand. Yet you feel the confusion of this sudden rejection. If it was God calling her, would there not be the light of God’s love in her eyes that would soften the pain?
Yet instead, she goes away for the retreat and comes back shut down and having to end it, and is not explaining herself in a way you can relate to. Its a cut-off from the moment she sees you. It just doesn’t seem very loving. And closeness to God makes one more loving, not less.
Instead, this sounds to me like what someone is like when they have found someone else. Its usually the someone else that makes them so sure this is absolutely over, when that comes on so suddenly.
My son broke up with his longtime girlfriend at end of August but you could see it coming since June maybe. I really think it was her choice even though they said it was both, or him. There was a long time of both of them gradually realizing they weren’t a match and the breakup was not a surprise. Neither of them had anyone else in their life, I would judge, and that is why it was a mutual pulling apart, not a dramatic where one suddenly pulls away and shuts down. When that latter happens, in my experience of observing, there is someone else involved.
So was this a mixed retreat - male and female? A retreat is a place where romance can bloom; it often involves fellowship, in a place where you are away from the cares and worries of everyday. People speak openly in group discussions, baring their souls, and you see people, the same people, when you are relaxed and feeling your best, and feeling open. And you share meals with them and you see them when you are tired first thing in the morning, and you are outdoors on lovely days going to the next group event together… those things promote intimacy.
Or was this a silent, directed retreat? That would point to closer to God, not others.
If it was more of a fellowship-retreat, I would wonder. If she is an honest person, you could ask her to tell you honestly if there is anyone else who has her interest - did she meet or spend time with anyone on the retreat that she feels she likes? And, I hate to say this, but look her in the eyes and see if she looks totally honest when she tells you. If she is telling the truth she should be able to continue to look you steady in the eye. And hopefully she won’t look left and up (as one does when creating a lie) or left down, (as one does when recalling a lie). (And it works opposite, looking down right means recalling a known truth and up right seeking a new truth from one’s mind). Yes, that is signs of lying that are pretty consistently-accurate with the average person (doesn’t work so well on a practiced liar, and I assume from what you say that she is not that).
If she seems to be telling the truth then you could also ask her if its more than God that is making her cut herself off so quickly and suddenly from you, is it that she thinks you are not the right person for her? It will hep you get over this if you have truthful and as full as possible information to work with, IMO.
It just seems that if she is truly drawing closer to Our Lord, then it should be easy to approach her for more understanding of why she wants to cut this relationship off. Don’t grovel, don’t overly emote how you want her back - accept her final answer (she wants to break up) but seeking better understanding of why should not be something that is denied you.
Oh, there is one other thing I think it could be. If you two have been sexually involved, or bordering on that, even, I can see how coming back from a retreat where she has truly drawn closer to God and therefore wants to be chaste would make her want to things off with you. If she wants to please God and embrace chastity and your relationship has been unchaste, turning her back on you, making a clean cut, and having little to say to you may seem to her to be the only way to accomplish this.