The wWoman I aAdmire mMost | pPart 1

Since it's a title, it needs to be capitalized, though there are some words in the title you don't capitalize, like; the, a, and, etc.

I have been always been fascinated by criminology.

As a little girl, I absolutely loved reading crime and thriller novels and watching documentaries about serial killers.

You can also say "When I was little"

And I still enjoy doing that.

Can also say "And I still enjoy those genres"
Just as a note, avoid using "and" at the beginning of sentences in formal writing. I know this isn't formal, just thought I'd let you know.

She was the first female criminologist, and she had a greasignificant influence oin developing the crime scene investigation in the United States of America.

"Great" works, but I think "significant" sounds more natural.
Can delete "of America" if you want, it's fine how it is though.

She was the first criminologist in US, you got it rightthe US.

Deleted it since you established that point two sentences ago.

So if you look onat her birth and death dates, you might notice that she lived during those times when women weren’t treated as equally as today, and feminism just began to flourish.

No need to add "as today", since we stated "during the time when".

Frances Lee was born into a wealthy family.

Her father, John Jacob Glessner, was an industrialist and a perfectionistic man, which could not affect the life of mother of forensics.

You're not wrong in saying "and a perfectionistic man". But, a more common way of saying that phrase is "and a perfectionist".
I'm not sure what you mean by "which could not affect the life of mother of forensics".

She had been educated at homehome-schooled by tutors; her brother went off to study at Harvard.

Instead of saying "educated at home" we can just say "home-schooled" to sound more concise/natural.

Frances also dreamed aboutof studying in the most prestigious university ofin America, however, Lee’s father didn’t allow her to further her own studies.

I think "dreamed of" sounds better.
"Her" is possessive of "studies", so no need to include "own".

Her brother’s classmate at Harvard, George Burgess Magrath, truly sparked Lee’s interest in investigating crime scenes and forensics.

It's a little wordy when you add "at Harvard". If you do want to add that he went to Havard, consider specifying that at one of the earlier times when you said he went to school.

He told Frances stories of real-life crimes that he assisted inhelped solvinge.

After her divorcement, she dioves headlongfirst into criminology.

Did you mean "divorce"?
For reference, "dove headfirst into" is an idiom.

She was interested in alleverything; murders, high-profile cases and investigations.

She even used to visit the places of death and autopsiesvisited crime scenes and the morgue.

Sounds a lot more natural like this.

Detectives used to destroy many clues, and some of themdetectives could not notice suspicious and evident things.

Your usage of "of them" is not wrong, It was just a little unclear the first time I read it, so it's just for clarity.

As such, many criminals went free because of these detectives ignorance and poor training.