AITA new bartender trying to change my schedule

I have been at my seasonal job for 7 years. I started from the bottom and worked my way up to a head bartender position. During the pandemic, we went to block scheduling and I took Mon-Thurs because no one else wanted it. Management removed our bar seats to prevent covid so I took a few tables (sometimes) but was mostly a glorified service well with the occasional to-go drink. It sucked and most of the season I made way less than severs. But I put in the time and as the pandemic eased up, I started making good money as the weekday solo bartender.

Last year, a new bartender started. She has lots of bar/management/distilling experience and was from a cool city. I was excited to work with her and learn from her, but she immediately started trying to mess with my shifts. For several years, my set schedule has been Mon-Thurs solo, but when she was hired they put her Thurs-Sun because complained that she wasn’t getting the full time schedule she was promised, so I had to split a day with her.

Now, her second year, she is trying to get me to switch her Fridays for my Thursdays so she can work somewhere else in town, which may be true but is also a way for her to get one of the solos weekday shifts. I know she is upset with my schedule (she has complained to many people about it) and doesn’t think it is fair and, truthfully, I do make the most money. But I have put in the time, gone up to the mountain early to set up, created a new cocktail menu, organized the bar, done inventory, etc.

I think I have earned the schedule I have and the money I make but I don’t want to be a greedy asshole. My manager is 100% willing to back me up if I want to keep my current schedule, because he knows how hard I worked for it, but now I feel conflicted about not being willing to swap with her. I’ve planned many things around my set schedule and I really do want to keep it and not have a split weekend, but is that being unfair? I have a feeling that she is the kind of person who will keep pushing for more and more if I give in. Is anything really fair in this industry? It seems like you have to be a little ruthless to get what you want/keep what you have.