TIFU by not making a move when the opportunity was there

Today I (25m) went to the cinema to watch The Odyssey (keep in mind this movie is 3 hours long) with my friend. We walk in and take out booked seats to sit down. Not long after, a group of girls come by (ages roughly 25 - 50) and sit in the remaining seats next to me.

So the pre-movie ads and trailers start, so I make myself comfortable and talk to my friend about some upcoming movies. When out of the corner of my eye, I notice the girl next to me taking quick glances at me. I ignore this and just mind my own business.

As the trailers and then the movie start, I notice more glances towards me, so I reciprocate the glance. I was intrigued. Due to the movie being long, I lean into the corner of my seat, away from my friend and towards the stranger. Not too long after, the girl next to me does the same thing. Coincidence, right…

The movie continues, and as it goes on, we move and shuffle around, but we always end up leaning close to each other after a while.

As the hours went by and the final act started coming on, I started to notice her quirks. How she would move around and adjust herself, her giggles, and her highly expressive excitement and fear she experiences when watching the movie. As the final act started to play and the tension of the scene started to rise, we began to lean into each other with barely enough room to fit a small box of popcorn between our heads.

As this was going on, I was thinking if I should say something to her, which moved to what I should say. The movie keeps playing, and we stayed like this for the final 20ish minutes of the movie.

Credits come on, and I quickly adjust myself, and as I’m doing this, I notice the girl does a triple take at me. I quickly look at her a few times without her seeing as well, taking note of everything, and my first thought was, “Hmm, she seems a bit older than me. I won’t say anything to her.”

However, I start thinking if I should say anything and then what to say. I turn to her to say something, but I just end up not saying anything. My friend and I leave the cinema, and a large, heavy feeling of sadness and disappointment came over me.

As we leave to head to our car, we stop in the foyer, and I see the girl walk past, roughly my age (give or take a couple of years), walk by with whom I assume is her mum and sister as she glances at me. I thought about saying something, but I didn’t. I had the perfect moment in the cinema. I knew it, and I didn’t do anything. I regret this very much.

Now for the lesson.
If you happen to be a person like me, one who sometimes is afraid of talking to new people and sees people making advances at you but decides not to acknowledge them;
You should ignore the anxiety, the fear. Because once the moment is gone, you will feel as if you missed an opportunity of a lifetime.

So take the chance, take the risk.

TL;DR: A stranger and I at the cinemas were looking at each other and spent most of the movie leaning up against each other but I chose not to talk to her and regret it.