It’s unspoken in LGB circles how everybody knows a “lesbian” who suddenly realized she was straight.

Yep. Women are the most likely to venture into exploring a different orientation but also the more likely to revert back to being strictly hetero, usually once her biological clock gets in.

And your statement is actually backed up by studies, which even the Left had to begrudgingly acquiesce, where it was revealed 80% of bisexuals marry into heterosexual relationships: https://slate.com/human-interest/2016/05/over-80-percent-of-bisexuals-end-up-in-straight-relationships-why.html

It's like being gay because it's trendy for a season.