<human>: Can you condense the text into three sentences or less?

My (22F) mom (late 50's) just opened up to me about how my dad (late 50's) had been exchanging emails with one of his employees (mid 20's) who is/was also really good friends with my sister. I guess he had been emailing her for about a month after which my mom confronted him and their relationship (she is no longer working with my family). My family chose to keep this all from me until now and I am the last of my 3 siblings to find out since I was away at college and they didn't want to tell me until I came home after graduating. 

This really just came out of the blue for me and I have always thought my parents had a wonderful and healthy relationship (they have been married 28 years) and never expected my father to do anything of this sorts. I just feel betrayed and feel horrible for my mom because I know she has been going through so much this past year and a half with other things in her life. My mom has assured me she doesn't want a divorce and has since forgiven him but wants closure since they haven't really talked about it too much since everything happened. 

Despite this assurance I still feel very weird about it all. I have always been a Daddy's Girl and respected my dad for being a great person/father but now I don't know what to think. Regardless, I just want to vent and want to know if anyone else has been in this situation and if you guys have any advice/words of encouragement.
<bot>: Dad had emotional affair via email with an employee who happened to be good friends with my sister. I finally found out about it from my mom (4 months later) and feel shitty and betrayed. Any advice?