My mother pulled crap like this with my niece and nephew all the time. She would breezily laugh it off. Or, when my sister-in-law was babysitting my younger siblings, mom made sure that part of the daily 'to-do' list was meeting preparation or reading from the Bible Story book. She knew exactly what she was doing. She told me so. Making sister-in-law read the Bible Story stuff with the kids, my mom saw this as 'captive witnessing'. She was so proud of herself.
Sister-in-law, on the other hand was not amused.
And the boys hated the forced bible stuff when they had a fun, non-jw adult they could play with!
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Separately, when I was 7, my parents were non-religious and had not yet begun studying with the JWs. Somehow (probably from kids at school) I decided that I really wanted to go to Sunday School. My parents found a church nearby and every Sunday morning would drop me and my little brother off at Sunday School. They did not attend with us. Just dropped us 2 little kids off. LOL. I was 7, my brother was 3. [Sounds crazy now. But I guess I was pretty mature for my age and overly responsible with my brother.]
I think we did the Sunday School thing for about a year before I tired of it. But the thing is, I think your 7-year-old may very well have shown an interest. (Could have been coerced. But not necessarily. I wasn't.)
However, the main difference is that JW publications first and foremost induce guilt and fear. Sunday School had us coloring Noah's Ark, Moses receiving the 10 commandments, the nativity. We learned a song to sing all the books of the bible in order. We sang "Jesus Loves the Little Children". And we played with other kids our own age. All the kids were together for about 20 minutes, then separated by age group for another 15 or 20 minutes. What we learned was age-appropriate and, to my recollection, never made us feel guilty or fearful.
It's the guilt and fear and sensationalization of godly-destruction that is so prevalent in JW publications that I would highlight to your parents. Maybe find and watch the video yourself. Or look at the other one on the jw website. Be familiar with them when you talk to your mom and let her know that you are working hard to raise a competent, curious, self-confident, intelligent young woman and carefully choose material that helps foster good values, and good morals, without triggering fear and guilt.
If your daughter really is curious about religion, without prodding from grandparents, you can find lots of stuff on your own online or at a bookstore. You can attend a non-demoninational church - this will give some friendship, too, along with the opportunity for community involvement/service. You can just read specific parts for the bible yourselves. Or you can tell her there is plenty of time later in life for religion and philosophy and that right now, her biggest job is to be a kid.
Good Luck with the JW grandparents.
-Aude.