Search Results: love taken out on context

I usually don't read educational books in English, but I stumbled upon one today. And I noticed the writer constantly referenced the reader as "she". Now, I couldn't help being thrown out of the experience by this, being a "he".
But more importantly, I was perplexed - who is this "she" the author is talking about? Why would the author take a side regarding the reader's gender? He (the author) could have just used a neutral plural "they".
Perhaps he is addressing the book to his daughter or other female relative or loved one?

Anyway, after finding a "she" for the 6th or 7th time in a row, I decided to look it up.

Turns out for the past roughy 4 decades authors made it a point to use "she" instead of the previous "he" as the default gender!
You might know this, but this took me off guard.
Personally I make it a point to always be impartial when talking about gender, so I always structure my sentences so that I can use "they", "one", "people", and when it is not possible, I write "he/she". So as you can see, I put great efforr into being fair.
So I don't really understand why an author woud have to pick a side in the first place. Personally, I feel that this approach, in the context I have read it for example (a mathematics book), is quite sexist.

Would you agree?

So the question is:
IS USING 'SHE' AS A DEFAULT GENDER SEXIST?

For a bit of context, I recently began flirting heavily with a girl. After a few months, things just didn't work. Turns out, weren't really right for each other. On the low-key, she took advantage of my kind nature, which is messed up.

What I did get out of this experience was one big question:

I found it difficult to make her laugh whilst being myself truly, and it's a big conflict of interest. I'm confused what's better, being honest and true to myself or straying from that for the betterment of potential love?

My sense of humour is very sarcastic, dry and ironic so that's what makes me nervous. Some people fail to pick up and then due to the nature of my humour I look stupid, but when it is picked up they usually like it?

I was just wondering what girls would think. Thanks!

I'm seeing a girl who I felt I was compatible with, sweet, kind hearted and had her morals straight. When things are good it's quite good. The flipside has been very hard. To start, she's not that educated but acts like she knows better and refuses to trust what I say is correct or incorrect, argues with me and even googles to prove me wrong, which fails. She is extremely hard headed, stubborn and prideful when it comes to arguments. Like an immature brick wall. She avoids answering my questions a lot when I'm calling her out on her shit or something that I felt was wrong, hurtful, or mean. She never admits when she's wrong. Like things we all know no one would like, she would lie saying she'd be okay with it, just to deflect her guilt. She is insecure, has daddy issues, threatened to commit suicide multiple times even if she has a son, doesn't remember important things I tell her and things we've argued about before, so stubborn to admit when one is wrong and then attacks me claiming I'm a person who always wants to be right, doesn't communicate well, takes things out of context, makes up what she thinks I'm thinking and doesn't believe what I'm actually thinking, so jealous and paranoid that I will run off with some other girl and straight goes into accusation mode and treats a faithful person like he's a cheater when she is a person who is overly friendly and taken as flirtatious (ie. greets random security guard with duck face puckered lips, eyes closed with hand gesture next to her eye like taking a photobooth sticker pic). It feels so unfair and she makes it like everything she does is okay but if I do something it's not or suspicious. Almost everytime she drinks she causes an argument/fight by getting snappy, angry, cussy. I feel so exhausted and drained. I feel like she is bringing the worst out of me. She says she'll change but we have the same fights and feels like she never will. She says she loves me but doesn't change what's destroying us. Is that love?