It's been a long time since I watched it but, from what I remember, IMHO she didn't like who she was when she…
I understand where you’re coming from tho. You explained really well how the spark wasn’t enough for her to feel safe or grow, and how the Love Alarm only showed instant attraction, not the deeper kind of love. I get why she chose what was healthier in the long run. Still, I can’t help but feel the second lead deserved so much better.