That's my thought as well... of course there's always the possibility that Elena didn't quite tell the truth to Layla, made up some reason for being "sad".
If Elena told the truth, Layla accepted it REALLY WELL, heck they even decided to tease the "unsuspecting" member of the triangle.
Like you say, it would make sense for the girls to be having a temporary spat... but that's not what we saw.
If Elena made some shit up... it doesn't quite make sense for her to be teasing does it?
Nothing has changed, Layla still doesn't know the full picture... so why is she having fun teasing the MC now when she was so uncomfortable being around them earlier?
About it fizzling out afterwards... there are ways to keep the tension going.
Future choices will have to strike a balance so neither girl feels like the 3rd wheel...
Can't bang Elena too much beyond Layla's approval

Neither can have Layla as the GF and Elena as "someone we fuck on weekends" if you wanna keep them both into it.
About this... a few pages back there was a conversation about how you can't break things up with Layla for Erynn.
I will add that you also can't break things up with Layla(or Alexis) for Nikki/Cara...
Worst still that you can promise Nikki/Cara that you will end things with the other girl you have been dating, but the option to actually deliver on this promise doesn't exist.