My investigation revealed that the song is https://www.youtube.com/watch?v=yLWitmmt0JA "Who are you" by Spring King. It is a pretty good song, certainly better than anything by Peaches.
Whether or not you personally liked the song by Peaches, I hope you can agree that that particular song perfectly matched Sarah's screwed-up mental state during that episode.
I'm always impressed by the music on Orphan Black. I've been introduced to quite a few songs I really like and admire from artists I never would have listened to otherwise.
I think it is a shame we got so much Peaches' music in season four and such a short snippet of the Spring King song. I got no feel for the song that way. Something more like this would have been nice: https://www.youtube.com/watch?v=gDhrbz6LnB0
Clearly, you and I think differently about music (and no, I didn't click on your youtube link -- you're entitled to your tastes and I'm entitled to mine).
I'm a similarly strong, independent woman to the sestras, and like Cosima, I'm a California girl. I had never hears of Peaches until that scene, but the moment I heard it, I didn't need the lyrics to make me want to rock out, and the lyrics resonated within every fiber of my... sisterhood.
Samantha Bee has chosen the same precise song as the theme for her political comedy?!?/however you describe her show, so I'm clearly not alone in thinking that lyrics like "the boys wanna be her, the girls wanna be her" and "I wanna be her" are precisely the anthem of the sestrahood of humanity depicted in Orphan Black.
I am not trying to belittle your musical tastes. The general consensus on this site has been that Peaches was a weak choice for a featured group, but it is nice to hear from people who disagree.
I am pro-Cosima as well, but this was a Sarah song. Cosima was planning to worm herself at the time.