That's what I posed earlier - Elena has never shown an evil side in this game. She can manipulate, but hasn't done so to the point of taking advantage of naivete or a tit-for-tat trade.
I think she'll use this information to get in D's panties more closely/often by leveraging the knowledge that D is far more sexually advanced that she's let on thus far. Elena will probably be more supportive of D and the MC's relationship + goals to leave than ever . . . but, she'll want to go with them, surely. I see that as her overriding goal emerging from this revelation and MFF would just be icing on the cake to her on that path.