Friend cancelling last minute, am I reasonable for being annoyed?

I'm always the one to initiate plans with 90% of my friends, and most of the time, I don't mind it. My closest friend never initiates anything.

One thing that's a pet peeve of mine is if someone cancels a plan that has been made weeks prior for no good reason. If something happened, if they're got sick, or if they got physically/mentally tired then I would understand obviously.

That being said, my closest friend and I work at the same job. She's a bit newer. Someone got called in sick today and they were asking in our group chat if someone could cover their shift, and I told her to remember our plans. An hour later, I see that she has accepted the shift.

She told me the only reason she did that was because she would feel bad if she said no. And I said that you can't feel bad for saying no to a shift you weren't supposed to work, but that it's rather disrespectful to cancel plans for that reason.

Am I being reasonable got being irritated? It's already hard enough to meet up with friends in the adult life lmao.