I Worked at the Same Company for Seven Years: From Office Assistant to Administrative Department Coordinator

I worked at the same company for seven years.
I started as an assistant and worked my way up to office administrator.
My best friend joined two years after me thanks to my recommendation.
I showed her the ropes, explained all the ins and outs, gave her the right contacts, and even covered up her mistakes at first so she wouldnt get the sack.
We had lunch together every day, went out on Friday nights, and I trusted her more than anyone.
Six months ago, they announced a managerial position was opening.
My boss told me I was one of the top candidates.
I began arriving early, leaving late, and took on even more responsibilities.
My friend kept saying, That jobs yours, you deserve it. I told her everything, even the strategies I planned to use for the internal interview.
On interview day, she turned up as well.
She hadnt breathed a word to me about it beforehand.
I realised only when I saw her waiting outside the managers office.
All she said was, I decided to give it a go. I tried not to think badly of her.
A week later, they announced the resultshed been given the job.
I just sat at my desk, staring at the screen, completely numb.
After that, odd things started happening.
As the new manager, she began changing processes Id put in place.
She pushed me out of certain responsibilities and started asking for endless reports that made no sense.
A colleague mentioned that shed said I lacked leadership skills, and many of the ideas shed pushed as her own were ones Id shared with her.
One day, I asked her straight out when we were in the break room, Why would you say those things about me? She replied, Its work, not friendship.
I had to make sure I got the role. I reminded her of all the ways Id helped her.
She just said, That was your choice.
I never made you.
Since then, the atmosphere has been dreadful.
She speaks to me coldly, corrects me in front of everyone, and piles on pointless work.
Some nights, I get home in tears, anxious, feeling like I just want to walk away.
But at the same time, Im angry at the thought of leaving without saying my piece.
Now Im at a crossroads: either keep quiet and put up with it to keep my job, or walk away and start from scratch somewhere else.
Would you stay, or would you go?