As lazy as it sounds, I think she just meant that Austin wouldn't approve of her exchanging numbers with another guy; specifically in the context of the scene (where you refused to take things further and actually swing with the couple). So, in this situation, Evelyn wants to escalate, but is pretending to follow Austin's lead and hides her true intentions.
Admittedly, the writing could stand to be better in terms of setting up plotlines and following them through, but overall, the end result is decent. Not good enough to make me sub, but mildly excited for future updates.