<human>: Give me the gist of the text in a nutshell

So around 2 weeks ago I hear my mother talking with my sister on the phone. My sister lives in another city over, 5 hours away, while I live with my mom here. Anyways, so I start hearing an odd conversation that went something like "How come you haven't told anyone?" "You knew the guy?" "Were you drinking". 

I thought nothing of it until I heard my mom telling my dad over the phone of the incident.

"She went to a party, even though her boyfriend told her not to, her boyfriend had to work so she went alone. She had too much to drink and was talking to a guy she used to know that lived in her old town. Apparently he took advantage of her and is now only telling me 3 years later."

"She hasn't told her boyfriend yet."

So I've learned that she kept this a secret for 3 years. Now just today my dad calls me sounding extremely upset. Which is strange for my dad I find he usually hides his emotions, and is never worried. Anyways, he asks me questions like "The last time you saw your sister was she acting strange? Remember when you were talking to her on the phone yesterday was she acting weird at all? She doesn't seem normal and I'm very worried about her." 

Obviously he doesn't know I know about the whole 'rape' thing I overheard so I say 'She's been very quiet recently'. So he asks me to email her asking how she's doing but be sure to 'not to mention me, and don't say I want you to email her'. 

So I emailed her and I'm waiting for a reply.
<bot>: I believe my sister got raped, and is going through depression especially since she doesn't have many friends out in the new city and to be honest I think she's fed up with her unmotivated boyfriend. Please help.