I completely understand where you are coming from. However your wife does have the right to talk with who ever she chooses. Having said that, I found myself in a similar circumstance in relation to my mum. In this situation I did intervene. I'll explain:
My mum left the borg with my sister and I around 2002-3. Since leaving we built up a good family unit, even though we were adult children. We were considered what do they call the split family in the 'truth'. ie dad wasn't a witness. Anyway since leaving it was good. My mum was the happiest she had ever been. While in she had been on and off antidepressants. Since leaving no need, just plain happy. Then tragically in 2009 she had a subarachnoid bleed in her head ( a massive stroke due to an aneurysm). It was graded as the worst and not expected for her to survive and if she did she would have major deficits.
Since we left the borg none of the JWs ever kept contact with us. But when my mum fell ill, the JWs heard about this and one of them an elder tried to pass himself off as her pastor at the hospital when she was in intensive care. I think they were trying to see is she was having a blood transfusion. We told the nurses there that he was not a pastor and that he does not have permission to visit her. The hospital ramped up extra security because he kept coming back and saying shit and he was spoken to by the hospital. He was the local elder for the hospital like a chaplain.
Then my mum miraculously recovered with vertually no deficits.
She was sent to rehab and the JW's found out. They started visiting and leaving WT and Awake mags. I took them without my mum noticing and threw them out. I spoke with my dad and got him to stand up for the first time against the religion and call one of the elders in the cong and tell himn that they are to make an announcement at the kingdum hell that no JW's are to visit mum. That she needs privacy as she is still recovering and deserves dignity. Also dad went off at him and told him that she has a head injury and is vulnerable and he does not want them using emotional blackmale on mum trying to get her back into the religion. And also that the use of guilt that the religion uses is not appropriate and will have a huge affect on her rehabilitation.
Dad got totally stuck into them, thankfully because I once being one of them couldn't bec Ive avoided being D'ed..
But it worked out well, they stopped visiting.
So having gone through this I totally understand. But your wife has all her faculties, although being vulnerable due to greiving. You need to talk to her too. Look after your marriage and nuture the relationship you have so that it is strong so those bastards can't get in between it.
Lp