<human>: Can you give me the gist of the text in a nutshell?

My girlfriend and I have been dating for 3 1/2 years and living together for 1 year. We have a happy relationship.

About 3 years ago I met a girl that I worked with, and as it turned out, we were both beginning relationships. We spent a ton of time together at work, really clicked, flirted all the time, but we were never more than friends. Still, I developed a crush that lasts to this day. Soon after I met this girl, my gf and I started hanging out with the girl and her boyfriend. 

We now hang out with them all the time, almost every weekend and often more. We go on vacation, spend some holidays together, and we are close friends.

I no longer work with the girl, but by coincidence, although we live in a pretty spread out suburb, we ended up working near each other. We talk on gchat every day and will meet for lunch or happy hour once or twice a week.

I realized the other day just how long I've had a crush on this girl. It's never gone away. I think she's crushed on me too, at least in the past if not now, and probably not to the extent that I've crushed on her. She definitely flirts back and seems like she's attracted to me. 

We are both in serious, long-term relationships, we both live with our SO's. And this crush just won't go away. It's been years now that I've waited for it to fade. Because my gf and I see them all the time, I have no idea what to do. I can't just stop seeing her without an explanation. Although I'm happy with my gf, I think about this other girl every day and can't wait until the next time I see her. 

Any suggestions of what to do here?
<bot>: GF and I are good friends with another couple, have crushed on the girl in the couple for years with no end in sight. How do I stop when I see her all the time?