Lol, enjoy joining the workforce when you eventually do and find out that positions have specific pay rates and ranges.

You can say it all you want but that doesn't make it true, people can and do do the same job and pay is tied to positions, have you ever held a job in your life?

If people aren't getting paid the same for the same job then yes it is inequality by definition

Why would she be mad at OP? How does that put a strain on the relationship? It's good information to know, now she knows she might have to look for another job or change something

I don't know why you're acting like you did something wrong, you should discuss payment info with your coworkers. We can't fight inequality if we don't know it exists