In fact, it gives her a thrill. Because of this, she tends to take high-risk bets in gambles, even if she has nothing to rely on but luck. Though this can sometimes end in her loss, she is emotionally unaffected by the results; she simply uses her loss or gains as a means to further indulge her gambling habit.
Yumeko is a wild hedonist, and in Hyakkou, she's like a bull in a china shop, much to the student council's dismay. Yumeko gambles not for wealth or status but for the borderline erotic thrill of it, and to her, gambling is something to be enjoyed on a raw and primal level.