Okay. Well, you cant exactly be angry at her for lying about this - you snooped through her e-mails, yeah I can KIND OF see why you did it, but e-mail accounts are personal. You're lying by omission anyway, so you're both liars in this case. Let all of that go.
If however, she comes to you or you find out for sure - that she is in contact with this person, then you are free to give her your honest opinion about it - but remember that she is free to have hers too, she will see who she wants to and you can do the same. Expressing concern and what not is reasonable, but don't go telling her what to do, if you do that - then there will be big lies and deception.
Just be yourself, it wasn't your battle in the first place and I don't think she needs to be rescued to be honest, if she falls down then help her up, but maybe this is a path she needs/wants to take.
To love is to suffer. To avoid suffering, one must not love; but then one suffers from not loving. Therefore, to love is to suffer, not to love is to suffer, to suffer is to suffer. To be happy is to love; to be happy then is to suffer, but suffering makes one unhappy; therefore to be unhappy one must love or love to suffer or suffer from too much happiness. I hope you're getting this down.