Her name is 虎丸星 (Toramaru Shou) and the kanji for each character are 虎 tora (tiger), 丸 maru (circle) and 星 hoshi (star). The reading for kanji is oftentimes different in names.
Actually, the first kanji should be 寅 (=also tora/tiger), but ZUN used 虎 once in the description of her boss theme.
They aren't; it just looks that way because the artist cut the numbers out of the colored pattern and/or outlined them, rather than constructing them as solid pattern like they did with the others. (read: the gaps you're seeing are actually the numbers, not the colored part.) I had to do a double-take, too.
Let’s see. Byakuren as flan because of the colors in her hair fade into another color like flan; and in Japan, it is children’s most beloved treat,and the screw, who love Byakuren are like her children . Shou with the checker cookies and wafer stick because the strikes in her hair and the tiger’s strip. Murasa with lollipop because the stick of the lollipop is like the handle of her ladle, and the swirl is like the water’s swirl that sucks ships in and sink them .Ichirin, obviously because cotton candy look like cloud- Unzan. Kogasa and Nazrin, I have no idea.