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I think you should give her some time to show you that she is changing if she seeks the counseling and also counseling from her Priest she needs both counseling from a professional counselor and her priests' guidance. If she can show you that she is trying and trying hard I would suggest giving her another chance but if she doesn't follow through with everything she said she was going to do to correct this behavior then I would consider leaving the relationship, it seems as though it was a learned behavior for some time and now that she realizes that she may lose you she wants to make things right so at least give her that chance. You don't want to look later down the line and find yourself living with regrets for not at least trying with her, if you love her some times you have to forgive like the bible says "Seven times Seventy."
It's just going to have to take time and patience and proof from her that she is truly willing to do the work to get your trust back. Don't expect it to happen overnight because this issue happened over some time and it's going to take even longer for you to trust her again and for her to regain that trust. I would postpone the wedding until you feel you can trust her almost completely before you set a new date.