Especially if you are the romantic kind of guy (absolutely nothing wrong with it, I am one too).

I know, it sucks. But the moment you see her becoming more distant or disinterested stop chasing her. Do not contact her anymore and put yourself first.

I'm not saying you shouldn't even try to resolve things. Maybe a little talk with her will help you understand better what is going on. However, if even after that she has always the same behaviours , just stop.

Do not ghost her, tell her simply how you feel (yes, do not be afraid to express your feelings, you should've told her way before arriving at this point) and that is better for you to focus on yourself because clearly, things between you two aren't working out.

And then focus on yourself for real. No stalking her on social media, no messages, nothing. She doesn't exist anymore to you. Go back to the point you were before meeting her and resume from there.

If you try to insist too much and force things you just become annoying. She will respect you much more if you leave her be. Plus, the probability of her contacting you again in the future is much higher, because you left things in an amicable way.

Do not hold a grudge, do not be angry. You do not possess her. This is just how relationships work, you should always cherish the good memories and go on with your life.