I've worked in many many nursing homes (agency and FT), and I avoid the homes that have these CNAs who are basically running the building because there isn't enough licensed staff to properly supervise them.
Because it is YOUR job to supervise HER, not the other way around.
Her behavior is NOT acceptable, and trust me, she knows it. She's playing a very in-your-face game of defiance and disrespect. The Powers That Be should have seen this coming and stopped it long before you got there, and since they haven't, and since you're a new nurse (not used to dealing with this stuff once and for all) it aint gonna happen.
This CNA is exceeding the boundaries of personal courtesy AND her job description.
Because her behavior has not been corrected by key authority figures, I would definitely start hunting for another job before she jeopardizes your license and challenges you at a critical judgment call. I would also tell the DON at your exit meeting that if they want to keep professional staff, they need to have CNA's who do what the charge tells them, and not the other way around.
Unless you wanna play power struggles in addition to your other duties when you're at work all day....
... and IMHO, who the heck needs that????
PM if you want.