Thank you for writing. I understand your concerns, especially with your history with your father.
Sadly, there is no way you can “make her understand”. It’s impossible to reason with someone who is irrational to begin with.
That being said, I want to assure you and are other readers that not everyone who suffers a traumatic brain injury has the same symptoms. Not everyone who suffers a head injury is filled with rage or is violent as a consequence.
I can’t tell from your letter how much of your neighbor’s behavior has been caused by the TBI or if she uses the TBI to excuse controlling behavior. Apparently, she can control herself at least at times.
As I read your letter, I had to wonder where her husband is in all this. Has he found ways to calm her? If so, it might be helpful to talk to him about his experience. And I had to wonder if she stays in control when your husband goes over there.
I don’t have enough information to give you concrete advice. I can only suggest that entirely withholding a visit with baby may throw fuel on her fire. It might be strategic for you to bring baby over for a brief visit but with both your husband and hers present to supervise her and support you. I don’t think she should hold baby because she is so unpredictable. You can plead “first time mother nervousness” for not letting that happen. Immediately leave if she starts to be abusive in any way. Tell her that you will revisit only if she can learn to control herself. This kind of preemptive visit will prevent any accusations that you never even tried.
If this continues to be a concern, you may need to consider moving. We can’t choose our neighbors. But sometimes we can choose whether to stay in the neighborhood.
I wish you well.