If you had really forgiven her you would not be going behind her back looking through her personal stuff. What she did was horrible , but you need to be the better person and not go through her belonging, emails etc without her knowledge. Be honest yourself and tell her. If you do not work out your trust issues, you will never be able to heal and trust anyone again you get close to. xox You deserve a relationship where these things would never happen. :-) GL and lots of love.
But trust shouldn't be earned by snooping around and sneaking. It should be earned with trying to believe the person won't do it again and talking about it. I was in the same situation and tree was no snooping or disrespecting their privacy boundaries. Just them knowing they lost my trust and had to earn it back so we talk it over often and try our best to fix the trust.
She destroyed a trust when she cheated.
She has no one but herself to blame.