kiwibunnies,

I wonder if your therapist has given you any tools to deal with your PTSD?  You said you do deep breathing but it has not been too effective.

There are a variety of tools that help with PTSD, e.g. EFT, EMDR, meditation, etc.  Have you looked into any of them?  Google those techniques for they seem to be simple and effective.

Who said you have to forgive her?  You can focus on healing yourself by focusing on loving yourself first.

Even if your husband does want contact with his mother, it does not mean you need to.  Even with family events, there is no need to go since it affects your health.  Experiencing PTSD trauma is nothing to fool around with.  Mental health issues are not taken seriously in this society because it is invisible but at least your husband be the one who should understand how damaging it is to you. Begging out of contact of any kind with your mother-in-law is tantamount in protecting yourself, your health.  Have your husband be your protector between you and his mother and the rest of his family.

Mark