My SIL cut off her whole family and is now making accusations about me. Is silence still the best response?

Hello Reddit, I need some advice/ideas on how to respond to this situation.

Lets get right into it. My sister-in-law (26F) has cut off her parents (my in-laws), all of her brothers and sisters, and me (her sister-in-law, 29F) over our reactions (such as an eye roll) to her lazy parenting.

By lazy parenting, I mean not packing them any shoes for a family trip, not changing diapers, not feeding them any healthy food, and not taking them to the doctor when they are severely sick.

BTW, we have all offered to help with the kids, and she acts offended and says she is the parent and she doesn’t need help. Then she will turn around and complain about how tired and stressed out parenting makes her.

We have all tried to reach out and talk things through like adults and meet up to potentially reconcile, but she refuses. The final offer was for family counseling to get through this, and her response was a letter to her parents and all of us complaining about how her brother, my husband (25M), and I get special treatment because we contribute more to the family and that we spread lies about her, which is not true at all.

We have spoken the truth about certain incidents, but we haven’t tried to berate her, made up lies about her, or even tried to make her feel bad.

What’s funny about this, too, is that we have actually never asked her parents for financial or any other kind of help. However, SHE and my brother-in-law have had to borrow $10K for his immigration, money for their wedding, and they let them live rent-free in their basement for three years. They have also borrowed money from other family members. She doesn’t work, and my brother-in-law struggles to keep jobs for more than a year at a time.

We, on the other hand, own a family business, and when we do spend time with everyone, we try to have fun and bring food or drinks to contribute. We also have a good relationship with my in-laws and the rest of the siblings.

Now, these past few months, my response to all of this has been to just not respond or reach out to her at all and just live my life. I was willing to all meet up and participate in family conversations, but nothing more.

I have never had success trying to build a relationship with her in the past, and I know she doesn’t know me or care about me or for me. But now that there are lies being told about me directly, I am not sure whether it would be worth it to write my own damn letter to her and let her have it for once, or if it would even be worth doing that.

Thoughts? Has anyone else been through something like this? Do I respond with facts for my own peace of mind, or do I just leave it be and let my lack of response be my final words? Any advice or help would be great.