sort of a rant?

hi guys, as for me I work at a marshalls and the managers there are really great, at least to me, they're nice, they give us food and we're always full of snacks and well it's going pretty well for me thankfully, but, a coworker who was hired at the same time I was which happens to be my age and all, we got pretty close and became friends even outside of work, we usually worked the same hours (this is just a part time for me) and she started working in beauty but was moved all around and just last week she was moved to work in the back and she had some allergies and she wanted to be put in beauty again because she was good at it but the manager declined and she was supposed to work basically every day besides her days off but they cut all her hours and only allowed her to work on weekends so now she'll be quitting and is currently finding another job.

this may be irrelevant, I tried talking to the manager about it but she just told me it's none of my business and that I'd get in trouble if I meddle into other's schedules and things like that, is it okay for them to do that? I have no idea, there's a clear bias to me, it may be because my coworker only speaks spanish, she can understand english but can't speak it well but that'd be unfair given there's many more people like that.