It is perfectly understandable that you would be angry. Your sister is violating your parental rights and encroaching on your role as a parent. Your sister is also interfering in your parent-child relationship, encouraging your children not to trust you . . . and to possibly defy you at a future time. And she is exploiting a weakness in your marital relationship for her own goals and purposes. I would be angry about that, too.
I had a similar situation with a relative who was trying to introduce transgender ideology to my very, very young children. My children are homeschooled, and this relative seems to think it is their “moral duty” to “enlighten” my kids so they won’t be “sheltered.” This relative also tried to introduce my small children to the idea of keeping secrets from parents. Since this relative felt they were on a “moral mission,” they would not back down – exploiting our family relationship at every opportunity as a way of trying to “enlighten” my kids (ie. at holidays, birthday parties, Christmas, etc.). I had to cut this person off completely. They are now allowed ZERO contact with my children. This has caused a rift in our family, as others blame ME when we all can’t get together for Christmas, Thanksgiving, etc. But I don’t care. My children come first. Raising my children in a Godly way takes precedence over the desires of adults.
After I cut contact with the pushy relative, one of my children’s grandparents (knowing my position) tricked me into a situation where that other person would have access to my children. I had to VERY firmly put my foot down with the grandparent: “You don’t have to agree with how we raise our children, but you DO have to respect it. If you insist on undermining our role as parents, then you will not be around our children. You will need to wait until they turn 18 to see them again if you cannot respect our parental authority. I love you, but I must do what I think is best for my children and my family.” I tried to be calm, loving, but FIRM. The grandparent apologized, admitted they were wrong, and promised not to pull a stunt like that again. So far, that has put an end to all that nonsense.
I know that what I did wasn’t “nice.” Maybe some people would think I’m “mean.” But it was necessary. God entrusted my children to me for a reason. If God wanted my relatives raising my kids, He would’ve made them the parents. In the same way, God has selected YOU, not your sister, to be the mother of your children. Some people will push and push and walk all over you until you show them that YOU are Mama Bear.
It sounds like your sister thinks she’s on a “moral mission,” as my relative did. If that is the case, she will not quit until you set some very firm and very clear boundaries. I do NOT suggest that you cut her off completely, the way I had to. But you do need to start thinking of some boundaries. Do you want to limit her access to your children’s phones and e-mails and social media? Do you want to limit her from seeing your children unsupervised? And if you think she is going to conspire with your husband to influence your children against you, do you need to keep her away until she calms down? I pray that the Holy Spirit will help you determine what boundaries are appropriate for your situation. Whatever you decide, you will need to:
(1) come up with a clear boundary,
(2) firmly communicate that boundary,
(3) clearly communicate what will happen if that boundary is violated, then
(4) stick to it.
Make sure you have that conversation at a time when your anger has subsided and you’ve had a chance to calm down. Pray before you have the conversation. And make sure you tell your sister clearly that you love her, even as you are being firm. “I love you, but I must do what is best for my children.”
This may also be a really good time to spend some quality time with your children. Your sister has attacked their trust in you. Now is a time to strengthen that trust. Maybe show them some articles and videos that support your decision. Watch and read them together, then discuss them. Maybe share with them some Bible verses about the end times, and discuss them together. They are old enough for in-depth conversations. Don’t leave them in the dark. If you don’t confront this head-on, the seed of distrust your sister has planted in them may grow. Draw your children close to you now and pluck up that nasty seed before it sprouts into a weed. Hold your children close and don’t let today’s events get between you and your children. I suspect your children will be heavily pressured at school from teachers and school staff about this jab. Even disregarding what happened with your sister, you need to make sure you’ve won your children’s hearts and minds when it comes to this jab.
I think as the day draws nearer, we are going to see more and more wicked attacks against children. And we may have to show our Mama Bear teeth more often. Being stern is not something that Christian women are accustomed to doing. But sometimes, it is appropriate. I don’t think that it is a sin to protect children. It is a sin to be unforgiving. It is a sin to hold a grudge. But I don’t think it is a sin to be a Mama Bear protecting her cubs. (And who knows? Maybe you are protecting your sister as well? Read Matthew 18:6 and Luke 17:2.)
Praying that the Lord will give you the wisdom and strength to converse with your sister calmly, firmly, and lovingly in a way that protects your children and brings glory to the Lord. Praying for healing in this relationship. Praying that the Lord will help you forgive your sister, even while you simultaneously protect your children as Mama Bear. And praying that the Lord will protect your children’s minds and hearts.