Advice on how to handle a pushy boss?

***EDIT***

I thought my post was pretty clear but apparently I need to state this again: I AM going into work every week for my SCHEDULED shifts on Saturday and every other Sunday. I have not called off a single time since I’ve worked here. I am just not able to pick up extra shifts like I was before this covid 19 stuff started.

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Here’s a little background info:

I had been a SAHM for 7 years when I decided I wanted a VERY part time job. The idea was to just get me out of the house a little and make a little extra money because I don’t like spending money on myself when I’m home all day.

When I interviewed for the job, I was very clear about what I expected and my boss said it was not a problem whatsoever. We agreed that I’d work every Saturday (10 hours) and every other Sunday (5 hours). So, 10-15 hours a week. Like I said, very part time. Those are my OFFICIAL hours on the schedule every week.

Well, I went through training and the very first week I was finish with training, she asked me to pick up a shift. It was just a 4 hour shift and I was able to so I agreed. For the last few months she’s been CONSTANTLY asking me to pick up shifts. Sometimes I say yes, sometimes I say no.

My husband is an essential employee and has to work longer hours now so for the last few weeks I haven’t been able to pick up any shifts.

She just sent me an email today saying:

“Hey, I’ve noticed you’re no longer willing to pick up extra shifts as needed. I was okay with you saying no on occasion but for several weeks you haven’t picked up a single extra shift. I appreciate that you’re here for your scheduled weekly shifts but you really need to start being a team player again. This is not the time to flake out on your work family. If you are unwilling to help out, we might need to consider termination of employment and I really don’t want to take it that far. Please respond with what shifts you’re able to pick up over the next two weeks.”

What am I even supposed to respond? I have told her that my husband has been working crazy hours and that I am UNABLE to pick up shifts but she still words it as though I’m UNWILLING to help out and I DO show up for my scheduled shifts so I don’t see how its even remotely okay for her to threaten termination. I really enjoy the job itself so I don’t want to quit but idk whah else to do at this point.