[AIW] for refusing to cover my coworker's shift for the 5th time this month

I work at a retail store in NorthPark Center. One of my coworkers — I will call her Jen — has asked me to cover her shift 5 times in the past month. The first two times, I said yes because I am a team player and could use the extra hours.

The reasons she gave:

1. "Family emergency" (I said yes)
2. "Car trouble" (I said yes)
3. "Not feeling well" (I said no — I had plans)
4. "Family emergency" again (I said no — I was suspicious)
5. This week: "I need a mental health day" (I said no)

When I said no the 5th time, she texted our group chat saying "Must be nice to not care about your coworkers." Two other coworkers liked the message.

Here is the context she does not share:

• I have covered 9 of her shifts in the past 3 months. She has covered zero of mine.
• She posts on Instagram during her "family emergencies." The second one was clearly at a Rangers game.
• Our manager is aware and has done nothing because Jen "has a lot going on."
• I am now being scheduled for shifts I did not agree to because Jen tells the manager I will cover for her before even asking me.

I finally told the manager: "I will not be covering any more of Jen's shifts. If she cannot work her scheduled hours, that is a scheduling problem, not a me problem."

The manager said I was "not being a team player" and that "flexibility is important in retail."

Jen is now giving me the cold shoulder. Two coworkers think I am being petty. One coworker privately told me "thank you, someone needed to say it."

Am I wrong for drawing the line?