Anyone with OHs is bad for Hitomi. I'd say her worst would be Mila, Leifang (Unshu and 3P+K beats the pants off of her) and Helena (that Bokuho goes under everything and can interrupt Hitomi's high-low strings)
Ayane does better against Bass, Hitomi has it tougher because she has to commit during the neutral. That makes it easier for Bass pick apart her play and make reads.