What happens to the other half of the white mana if I pay half a white mana for Little Girl?
Oh, I get it. You’re hung up on Comp. Rule 104.1 (The _Magic_ game uses only natural numbers. You may not choose a fractional number, deal fractional damage, and so on. When a spell or ability could generate a fractional number, the spell or ability will tell you whether to round up or down.). Yeah, we don’t follow that rule in Silver-Bordered Land. If you take three-and-a-half damage, you drop to sixteen-and-a-half life. If you then pay half a life, you drop to sixteen. As for that half of white mana, if you don’t use it, you would burn for one half and drop to fifteen-and-a-half life.