In the very early first couple of years of my marriage my mother-in-law took it upon herself to send me a bunch of leaflets including a copy of Humanae Vitae basically implying that we were using ABC. I was really devastated by this behavior.
- Because it was none of her business, this is an issue between husband and wife and to think she was obsessing about our sex life was :nope:
- It hurt me so much that she assumed that I didn’t know what the church taught OR that we would willfully go against church teaching.
- It reinforced previous impressions that she did not care about me personally as a new family member as much as my potential to produce the first grandchild.
We were not using ABC but I didn’t tell her that. I just mailed everything back with no comment.
You have said your piece, I would really advise against producing lots of paper for her to read. Respect your sister, respect the boundaries of her marriage. Pray for her and talk kindly to her IF she brings up the subject herself, otherwise do not become the police patrol of other peoples private lives. Pray before you act and ask yourself if what you do comes from love - will your sister receive it as loving? If not, lecturing her will be unlikely to produce the result you are hoping for. You do not know how your comments could be received and it could damage your ability to reach your sister with the gospel.
God bless you.