My mother in law was a busybody until I stopped giving her information. The last straw was when my son was having trouble remembering to potty and she told him it was ok to pull his pants down and water the garden. I sew on Sunday. I do not consider it "work" and all my obligations are met.
Ask yourself what her motivation is.

Yes if I am going to have it ready to present to someone in my church.

My husband watches sports and sometimes I quilt!

I sew or quilt almost every day of the week. It depends on what project I am working on.

My father said his parents had two sayings:

"Sew on Sunday, weep on Monday."

"All the stitches sewn on Sunday would have to be picked out (using your nose!) in hell."

Sundays are the day that I do my best quilting....so yes I do quilt on Sundays.

Growing up strict Catholic I can remember being told I was playing too hard for a Sunday (guess we were having too much fun). No work was done, however, mom had to fix a big Sunday dinner. Wasn't that work???? I'm thinking that sewing was being looked at as work not for enjoyment. No stores were open (grocery or apartment). Times have certainly changed.

I suppose your MIL doesn't shop or cook or anything else on Sundays either?

If you did quilting for a living, yes, you should take a day or two off every week.

yes, I quilt when I feel like, and I agree, getting old sucks.

I work 6 days a week outside the home and sundays are the only day I can get down and sew.