Obviously a posed candid shot at some home party (just check out the bottles on the counter). The "CF" looks older and, besides both breasts, also has both purse and cell phone in her grasp.
My guess is that the NF is celebrating something like a 21st birthday or graduation and getting a little wild. The CF is an older relative, possibly a sister, who has just arrived or is about to leave, and decided to take a fun shot.....while playfully 'covering up' the exposed goodies.
Again, this isn't the weirdest one I've ever seen, but I like the tone in it.