From my experience with covens there are few, if any, that are dedicated to a specific area of focus. As you will see, most of the covens here have very wide ranges of topics that they attempt to cover. If I had to recommend the best coven for what you're looking for I would have to suggest Penta Magick. Although I haven't been a member of their coven, I do have a lot of respect for both the leaders and members of the coven. They also have a smaller area of focus than most covens, one of the areas being healing. (As listed on their coven description page.)
Try messaging the leaders of the Penta Magick coven and ask about what they have to offer on the subject of healing.