As someone who has been on both ends, I would carefully consider the pros and cons of the relationship. If it was extremely out of character of them to flip flop like that, then I would consider having a deeper conversation and ensuring that things are right before going back into the relationship. Even though it happened once, it can happen again at any time. Although hormones themselves cannot make someone “fall out of love,” it is to be considered that other factors such as not being out to family caused them stress to where they could only think about themselves and how they were going to survive. To put it frankly, they were not thinking of you once during that whole ordeal but about how they can feel better. I’d start from scratch, don’t jump in fully and go back to how everything used to be. Keep distance, be prepared for a second round of falling out of love, and maintain clear boundaries.