AITA for not covering anymore shifts for the other girl at my workplace?

Hi there. At my workplace, there is only 2 of us girls that covers nighttime work (i do Tuesday-friday 12am-5/6am) and the other girl does Saturday-Monday, usually the same times.

over the last month, the weekend girl hasn't been turning up and i have had to pick up her slack and its getting a bit beyond the joke now, i dont usually plan to do anything on my days off. But its still very frustrating when i will be at home spending time with my partner and i get a message from the other girl asking me to cover her, cause she's got a headache or stubbed her toe or just something that is just dumb.

when i asked her to cover one of my shifts in return for doing one of hers, she makes up excuses or doesn't. This weekend i planned on seeing my grandma and she cancelled on going to work, so now i have to cover her (my boss didn't ask me, i was forced). Im at my wits ends, cause this has been going on for a bit over a month now. I like my days off too and it makes it feel like i can't plan weekends, cause i dont know if she will turn up or not.

i did send my boss a message and said “i will this time, but after Monday, i won't be able to cover her anymore. I have plans outside of work on my days off and had to reschedule them, this time. Next time i won't be able to”. My boss said “okay, thanks. Tell me what your plans are next time, cause i dont know”. I was thinking ‘i shouldn't have to, since they are my days off’.

i am planning on using my weekends to catch up with family/friends and making mondays my days to see my therapist, i do try and make plans on my days off. But figured if i have mondays unavailable the weekend girl will have to woman up and do her work, i understand times can be tough. But I've never asked her to cover for my shifts. But she dumps all of hers onto me and as you can imagine, im annoyed. But WIBTA if i was to stop covering her?

AITA for not covering anymore shifts for the other girl at my workplace?
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