http://www.novoteltaipeiairport.com/tw/ is the hotel and it actually has its own Airport Metro stop. Apparently, there are some places throughout the terminals that people can sleep:
https://travel.ettoday.net/article/5...96%93%E3%80%8D
There is/was an air-side hotel at T2:
https://www.plaza-network.com/locati...rt&city=Taipei
I would think BR at DPS should let your friend check the bag to TPE but only do so if your friend will enter Taiwan.