As someone who has dealt with a lot of my own trust issues (stemming from my childhood) around my husband and opening our marriage up, (unwarranted as they were) I think counseling is the perfect answer. For me, when it first came up, I had to put polyamory on pause for about 6 months, while I figured me and my shit out. I knew I wanted the open marriage, and wanted it badly enough to face my own internal demons to try and fix myself and my issues.
Throughout my processing, XIV was ever supportive, and would randomly launch discussions about my feelings, how I was feeling, how I felt about polyamory, how I felt about life and my own processing I was doing. He wasn't pushy about it, but asked just often enough to keep the discussion open. Our communication VASTLY improved in that short time period, and I now feel absolutely solid in our relationship, in a way I didn't realize I was feeling shaky.
I'm sure with time, your wife will be able to process not just her trust issues with you (however valid or invalid they may be. Mine were invalid, turns out lol) and what I'm guessing are overall trust issues in general.
One of the weirdest things I realized through my processing, was that while I was pointing the finger at XIV and saying "I don't trust you", the bigger reality was I didn't trust myself. I didn't trust myself not to leave, not to break him and I and our relationship, not to break boundaries, not to hurt him before he could hurt me... all very destructive things, obviously. Realizing that and working through them was like an "A-ha" moment for me.
Do I still occasionally have some jealousy? Some. Freak out every once in awhile? Yep. But I'm human, and I over-analyze EVERYTHING. Working through my issues allowed my relationship with my husband to develop to a whole new level. I hope, (and I think it will) do the same for you and your wife. Good luck, and keep on reading. Encourage her to read and research on this forum and other sites as well. A few of the blogs really hit home for me and helped me figure some stuff out. There was one specifically that flipped a light switch in my brain. I'm trying to remember which one it was... if I think of it, I'll respond again and let you know.