Hi, firstly you are not alone, far from it. And am so sorry that you are going through this.
This withdrawal without explanation is a torment and I can imagine how desperate you must be feeling.
Your husband, however, could be right, your daughter may come round, and if she only does so in order to communicate with him you might get a better idea of why she is doing this and he could help find a way for the two of you to speak again.
An accusation of mental illness is cruel inasmuch as even if you are mentally unwell it is hardly your fault and sympathy rather than an accusation are in order, but to make this accusation without any foundation in truth shows that your daughter only wishes to hurt you right now, for whatever reason.
In any case if she is saying things like this right now is better if you are not communicating for the time being and if your husband and siblings keep the lines of communication open.
You mustn’t lose hope. 6 months seems like a long time when you feel so hurt, but it really isn’t, there is time to repair this so stay strong. But whatever you do don’t feel so reduced due to her withdrawal that you accept any kind of reconciliation, remember it must be on your terms as well as hers, and she owes you an explanation and apology for putting you through this.
Give her too much leeway and you will leave the way wide open for her to do this again.
I really hope you manage to sort this out.
All he best xx