Never let the small sample size of your immediate boss and past bosses be the guide to how good you think you are. There is a chance she was picked on, because of some subconscious bias. I’ve had some shitty bosses that have given me awful references and other glowing ones. Some expected me to code as per job spec, others wanted me to be something like Gordon Ramsey off kitchen nightmares turning some fucked up situation into gold overnight.