Riva comes with LR attys. LR cartos are better though - more consistent, need juice less often. Cartos are awesome. For 510 threading Boge are most popular and the 2.0 ohm LR ones are the hot ones. I recommend learning on the standard res. Atomizers just suck so bad when they get gunked up - lose flavor, lose hit. Pain to clean. Every carto has its own fresh atty.
I am just suggesting she try the juices I found out of everything I have bought, that have the most TH.
Is Kgo a real 3.7 device? Or 3.2-ish like Ego? From what I read it is a real 3.7. I am trying one of those clone Ego 3-stage batteries from GotVapes (3.2 (ugh since I use standard res Boge cartos) - 3.7 - 4.2). Feels good fully charged but I just got it last night. It remains to be seen how well it holds the voltage up.
BTW - if you have the a 901 or KR808D-1 threaded Kgo (the Kanger one) then you should not need an adapter to try those cartos I mentioned.
And don't beat yourself up or give up.
I have (and love) my EGO PT but it doesn't hit nearly as hard as my KGOs. This is a short, interesting vid on the KGOs power v 18650 AW batts
18650 and KGO on volt meter: hoosierecigsupply.com 1100mAh eGo battery whips AW 18650 IMR - YouTube