Should I continue attending this group?

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There is a female colleague I met through a certain social group. I had feelings for her, and although we weren't very close, we got along reasonably well through small talk.
Just as I was about to show my interest a bit more.... I heard that the leader of the group is dating her.
It felt like a bolt from the blue.
And now I'm hearing news that they are planning to get married soon.
Because of this, I am wondering if I should continue participating in this group.
Of course, I don't have feelings for her anymore. However, if I go to the meetings, I will see her... and it leaves me with an uneasy feeling, and I think I'll be reminded of my past self who couldn't muster the courage.
Also, I'm not that close with the other members.... so I'm questioning whether I should stay.
The group isn't just a small hobby group or a drinking club; it's more like a university club, and it's the kind of group that can be helpful for networking or for my career and economic prospects.
Anyway...
1. Just leave the KakaoTalk group chat quietly without saying anything.
2. Forget the past and try to get along with the other members and that female colleague.
I am torn between these two options and unsure how to act.
Am I being too narrow-minded?..