Maybe I'm not single anymore
To put it another way, if the accident of falling into the water had not happened, could she guarantee that she would have some relationship or intersection with Ash later?
It's hard to say.
But one thing is undeniable. She had a long-term crush on Mark. If it hadn't been for that accident, she and Ash might not have been apart for ten years before meeting again. Countless possibilities will be created due to a combination of circumstances.
No matter what happened in the past, and no matter what assumptions are made now, if you miss it, you will miss it. No matter how profound the past is, it has nothing to do with the present. It is just the past that created a beautiful memory for her. She can clearly see who the person in front of her is.