Leliana and Cassandra have been through adventures where they questioned the status quo. Vivienne worked her way up within the confines of the status quo and became successful, turning the position of court enchanter to something more than a joke. She already pointed out that not all Circles were the same. Kirkwall was by far the worst, but it shouldn't have been the proof they needed to break up the system, in her opinion. In fact, all the past blood mage encounters give a strong support for the need for Circles rather than the opposite.
Which comes full circle to what I initially said that got us in this exchange: She wants to maintain the status quo because she's living like a queen under it, and who wouldn't want to keep that.
There's nothing overtly wrong with that, if it were me, I'd want to maintain it too. Under the Status Quo, she's not really living under the rules of the Circle, or even under the rules of the Chantry concerning magic. To wit:
How we're introduced. She freezes mouthy boy, and, if you demand it, will kill him with magic. The only person being "served" is the Herald, since you can let her deal with him, and he embarrasses him and sends him on his way, but it is an option.
She can become Divine. Mages aren't allowed to hold titles or land in southern Thedas, because that's magic ruling over man. So by becoming Divine, she not only doesn't preserve the Status Quo, she turns the whole thing on it's head. I don't know what happens in the epilogue screens if she becomes Divine, as I said, she hasn't gotten that yet, but that's a pretty glaring change to the Status Quo.