Find a new job. Your situation won't improve unless you make an effort to change it.

Gotta love politics!

perhaps they have more experience mangering and just needed to know how things work.

Have you been in the same position for those 10 years and or showed any self motivation to up skill to be considered store manager material?

I know people who have been in jobs for 10+ years too but they literally know nothing about how the business works outside of their role.

While I agree with promoting from with in a company. I don’t think that the person that you trained for 6 month over passed you for no reason, and it possible that she was hired to be the store manager.
My suggestion would to maybe find out why you weren’t promoted and then go from there. I wouldn’t just quit because you didn’t get the job, but that’s your choice also.
In a previous Job I worked I tried to be a manager and I spoke with the owner, and she went over with me why I wasn’t ready yet, there was a lot more things that I would have to deal with and after talking with her I realized I wasn’t ready also. I believe in doing a good job and if she promoted me at that time I would have been the employee that I wanted to be.

Amount of time does not mean you deserve promotion over another. Are you management material? Have you made it clear that you were even interested in a management position. I think it is important to set goals and be clear with your peers career goals.

years don't equal entitlement.

Then she was hired on as store manager and probably either has more experience or more qualifications

dick got sucked somewhere along the line

Which of you has bigger tits?