The sex scene with Elena seemed gratuitous. It felt like Elena was tacked on to the update simply to make an appearance.
Elena shows up, has sex with D, then she has to bolt off.
IMO if the scene with D+F+Elena was unneeded, it was just a repeat of their last threesome. F commented it was nice to be away from the girls.
It should just have been D and Elena having sex with each other. While that option was available it was again same D+Elena sex different day. There could have been greater character development for D if she had had actual sex, not just D laying there and letting Elena get her off. D has had lesbian sex done to her from other girls, this could have been the time for D to become as aggressive with girls as she is with F. At this point in her sexual life D can not realistically doubt she is into girls as well as guys.
Maybe this is the pitfall of having too many paths, too many irons in the fire. At some point every path would need it's own update for the path to have any meaningful advancement.