Q: I accidentally synced my friends phone with my iTunes account and now her phone is a replica of mine. How do I delete my stuff from her phone and recover her stuff?

The device is linked to one Apple ID and only one. Since you have been the first using yours to sync, then she will see all what you have: apps, movies, songs, etc. So you need her to sync with her own iTunes and Apple ID, keeping all the info so she does not lose anything.

I would recommend her to create her own Apple ID (you can do that in https://appleid.apple.com ) and then you can turn on Home Sharing in your iTunes at the menu bar > File > Home Sharing > Turn On Home Sharing so she can listen to your songs when you share the same wifi network.

Yes, there is. Make sure she has a backup of her information, then plug in on her own iTunes and follow the steps in this Support Article:

How to erase your iOS device and then set it up as a new device or restore it from backups - Apple Support