Was I a rebound?

I’m struggling to make sense of a breakup that completely blindsided me. Looking back, I know relationships don’t end overnight, but I was not expecting this. She spent months reassuring me she loved me, wanted a future with me, and made plans for us together. Even in the days leading up to the breakup, she was still telling me she loved me and acting like we were building a life together. That’s why it felt like it came completely out of nowhere.

My ex (24/F) and I (24/M) dated for 4 months. We started casually because she was going through a major life transition, but things quickly became serious. She told me she loved me first, talked about a future together, reassured me constantly, and made me feel secure in the relationship.

Then things became very confusing. She had unresolved feelings for her ex and started going back and forth between wanting a future with me and questioning whether she was ready for a relationship. There were moments where she fought for us and made it clear she didn’t want to lose me, followed by moments where she seemed completely detached and unsure.

Out of the blue, she ended things, saying she needed to figure out who she was on her own, wasn’t sure she could give me what I needed, and didn’t see the relationship working long term. We didn’t have any arguments or communication about doubts, she dumped everything and left. Later, she reached out saying she missed having me in her life and wanted to be friends, but I declined.

The hardest part is the whiplash. Someone who made me feel loved, chosen, and like we had a future suddenly felt like a completely different person. I’m struggling to understand if I was just a source of comfort during a difficult time in her life, or if she genuinely loved me but wasn’t emotionally ready for a relationship.

For people who have been through something similar: how do you tell the difference between someone who truly cared but got overwhelmed, and someone who was using you as a temporary emotional replacement?