Yes, I didn't know it because I followed the harem path and she doesn't appear on that path but now that I am trying the individual routes, she indeed reaches out to each girl and we meet her.
We don't meet her on the harem path, we meet Sabrina's mom instead.
But since the author basically abandoned the story and rushed the endings, there is no development with Evelyn nor with Sabrina's mom, which I find very disappointing since they picked my curiosity too.

I followed Sabrina's path just as much as every other girl's path, I followed the harem path, and this threesome is mentioned on the harem path but never actually was shown, it is merely said that it happened but it was skipped.
Do we get to witness Sabrina's first time if we follow only her from the start?

Sabrina doesn't have her own path, she can only be part of a harem who includes Miracle.
There is no Sabrina without Miracle, which I find unfair as she is the only one to not have her own individual path.
But then again, the author quickly abandoned the story so it lacks A LOT of developments.

Oh, now that I tried the individual routes, I got it.
When the narrator told me that the general story was done and I had to choose which route I wanted to follow, I chose the harem path.
BUT! The individual routes are not alternative paths, they actually form a continuity so if you get straight to the harem conclusion, you miss parts of the story.

The threesome with Sabrina and Miracle mentioned in the harem route happened in Sabrina's route and Sasha and Paris were away in New-York because Sasha got the role in Sarah Green's movie, which happened in Sasha's route.

Also, this threesome is Sabrina's first time but it is not Miracle's first time, they acknowledge that Miracle had her first time at the hotel, the confusion comes from Sasha who says in the harem route "you wanted us to be present when you got your cherries popped?" but actually only Sabrina got her cherry popped as Miracle already got it earlier at the hotel but maybe Sasha doesn't know that.

So in order to get the whole story, we have to first follow Sasha's route in which we fly to New-York for Sasha who auditions for Sarah Green's movie, then Sabrina's route in which Sasha stayed in New-York to organize with Sarah Green and was joined by Paris who went to meet a famous MeTuber to work together, which leaves us alone with Miracle and Sabrina at home, when we get a job on an island and we fly there with Miracle and Sabrina and that's where we have our threesome.

Which is Sabrina's first time.
THEN the harem route which concludes it all.
There are some inconsistencies between the routes but they form an overall continuity, the author fucked up when he asked us to choose a route because they are incomplete without the others, he would have better continued the story in a linear way, that would have been less confusing.