Her relationship with this guy is not a friendship, it is an online affair. She has become emotionally and sexually attached to him, infatuated and a little obsessed which is why she was selfish, spoke to him every day and pretended it was "no big deal" overlooking your feelings and pretending it doesn't affect your relationship. She was in denial.
I think you should be aware of the potential risk and damage this could cause to your relationship if she doesnt keep away from this "friend". She will be tempted to contact him in secret so be aware of that. I dont think your little chat was firm enough and she should be aware of the consequences of carrying on her little fling. You should tell her in mo uncertain terms that you and her will be finished if she ever gets this close to a guy again. Also ask her to research emotional affairs so she is fully aware of what she has done.
Dont just brush this under the rug. Your not in the clear yet and you both have work to do to save your relationship. If there is anything missing (romance, intimacy, quality time, communication etc) then you should be working on fixing it now. It may also be s good idea to buy some books that you can both read such as "how to avoid affairs" or "saving your relationship" etc
im not trying to scare you but this is a red flag and you need to be aware that she may continue to talk to him discretely because these affairs can be addictive. Its an escape from real life, an unhealthy distraction from all the stresses and strains which can delude people so bad that when they finally come back down to earth-they only realize then the destruction and pain they have caused. Communication is vital and a few sessions of couples counselling may do you the world of good
best of luck
"Don't ask a question if you can't handle the answer".