Perhaps Billy is the white hat she hired to do it. She called him a computer guy.
She consulted him to setup her office IT network while it was being renovated hence why I had to work in her apt.
He must be Chinese because I noticed Chinese characters coming up on WordPad documents on the 2nd computer before I changed the router.
How much did she pay you?
Did I tighten down the new router to the correct settings? Having trouble getting through?
That would make Billy a black hat, not a white hat.
Either way, I'm having a hard time believing your router was infected at all. It just sounds like, if what you're saying is true, she installed a RAT on your device... most script kiddies like to use Poison Ivy since it's so easy to use. The only--if not most likely--way she would be able to access / configure your router settings is from your laptop, utilizing the remote access functionality of the malware, and assuming your router used a default password.
The fact that you claim you saw passwords and other credentials being manipulated in front of you tells me that she had remote access to your device, whether through a RAT or by leveraging RDP (although if you're behind a router this is unlikely, unless it occurred while you're on the same network as her).