SgtScream :
If you sister has a youtube channel and has to stream content while gaming (on the same machine), i'd suggest going with an intel core i7 as a bare minimum. What's your max budget?
Budget for her is under 800$ also I picked a micro atx case because she wants it to be small
CPU: i5 7500
MOBO: MSI B250M Pro-VD
RAM: Crucial Ballistix Sport 1x8 gb
SSD: Kingston SSD Now UV400 120gb (she may want a Seagate barracuda as well)
GPU: Geforce GTX 1060 6gb FTW Gaming
PSU: EVGA either a 500w or a 600w I might be getting a 600w tonight on sale for about 35$
Case: Thermaltake Core V21