My take is they all pretty friendly to each other. Dasha wanted a free vacation abroad, so M&S took her in. There's little sexual chemistry between D and M&S. D does not seems to be into girls beyond some superficial cuddling. She might as well have a BF waiting for her at the Motherland, and perhaps that's why there's zero flirting and PDA between D and S.
The girls are gorgeous though, so it's still all fun and games