If you are buying for a bachelorette: party games, played with clothes on. Charades, bar cards and question decks work in a room full of people. Couples decks do not, and somebody will quietly put it away.
If you want it played more than once: buy a mechanic, not a prompt deck. Dice and tumbling games come back out of the cupboard. Prompt decks generally do not.
If starting the conversation is the hard part: dice. Nobody has to suggest anything, which is the whole appeal, and the randomness gives you both an easy out.
If it is a gift and you do not know them well: novelty over explicit. Pins, candy and a bondage teddy bear get laughed at and kept. An explicit card deck opened in front of the wrong audience is a different kind of memorable.
On what to check before you buy: the player count, and whether it has to be read aloud. Those two things decide whether a game gets played or gets shelved, more reliably than the content does.