I get a sense its more her celebrating turning 23yo with her two bffs. She's happy, which is very rare, and so she is merely seeking out the most amount of positive approval/attention she can get on this happy occasion. Understand that the easiest way a girl can get a lot of attention/likes in a room is to wear tight clothing and/or show cleavage. So this post is merely to seek out positive comments and high upvotes on her twitter feed, which it undoubtedly will. Sure it is not Brittany, well, not Brittany year 2018+, but think of it as when girls "cheat a little" by eating ice cream late at night; it makes her feel good to drop her bitterness/jealousy/morality issues for a little while. This will likely be the last time you see these mammary glands after today.