Aww, you poor thing...this too, shall pass.
Actually, it sounds like your pup is on a good schedule since she's consistent and getting up only once a night at 4 months old. Maybe you could keep her up past 8 (a little later each night) until she's closer to your bedtime? Then you'll get closer to 5 hours in one stretch before she wakes up. But before you know it, as she get bigger and physcially capable of holding it, she'll be sleeping through the night. And withholding water for a couple of hours before she goes to bed it a good idea, but just be sure it's not too long, especially if she's tiny. Great job, keep it up!