Woman time travels to kill people in the past???

It kind of sounds like "Millennium"

https://moviechat.org/tt0097883/Millennium

I think there was a 90s Outer Limits episode about something like that. There was a tall woman with short hair investigating some bizarre murders that had taken place in the 80s, and the murders all pointed to a strange woman working at a local university. But the murders made no sense, because they took place when the professor was a little girl, and living far away from where the murders took place.

You then find out that the professor had built a time machine that only some people can use, people born with a unique brain setup. In fact, the opening scene in the episode is where the professor was giving a lecture on fetal brains and proposing that maybe some dissections of aborted fetus brains could be done to examine this unique brain trait, but the class got disgusted with her and the lecture was ruined.

So then, you start seeing this professor using the time machine secretly to go back in time to kill men who had sexually abused various women, and/or murdered them. She was basically trying to stop these men from doing the crimes before they happened. She was doing it as revenge after the cruelty and sexual abuse she suffered as a young woman.

What made things particularly messed up was, she's trying to right wrongs through time-travel, but the machine is slowly damaging her brain over time with each use. The investigator (who also had the unique brain trait that the professor had, so she could use the machine too) eventually found out the truth and decided to help her, but the professor died in the past when the investigator finally killed the man who made the poor professor's life hell while growing up. In fact, the entire timeline was changed as a result of this.

The next scene shows the investigator coming back to the present, and it took her a while to find the changed professor, because she was almost a completely different woman in the new timeline. She was happy, took care of herself, pretty, was hanging out with kids and engaging in crafting hobbies, etc. The investigator then reintroduces herself, and still somehow managed to befriend the new version of the professor, and asks her if she still built the machine, and it turned out she had, but she had seen no need to use it.

So then the show ends on an ominous note, because the investigator is now the one using the time machine to go back in time and shoot men who abused/murdered women in the past. She basically continued what the professor originally started.