In the Heartstrings universe, they don't even have words like lesbian, gay, etc, since they know it's pretty much pointless to segregate based on sexual orientation. If it comes to that, they just say "I'm not into colts/mares." Love is the standard. :3 (As long as it's between consenting adults ofc, (though i guess it's not shunned upon when two teenage ponies date, but bigger gap in age can rustle some jimmies.))
They'll get married in about 60 chapters, don't worry. :3
Well, I made that comment in light of the TV series, not the Heartstrings series (which I hadn't been reading at the time I made that comment). It's nice to hear that they don't discriminate based on sexual orientation in the Heartstrings version of Equestria, though.