Stella seems to be very temperamental about her husband's infidelity to the point of verbally and almost physically attacking him while screaming, breaking a lot of possessions and even assaulting an imp butler.

However, she seems to be more baffled by said infidelity specifically happening with an imp, a demon of lower position; she is also incensed that Stolas spoke of his inability to go to a motel to consummate it. Given Octavia's indifferent attitude towards her aggressive outburst, it can be assumed Stella has these outbursts on a frequent basis.

Given her choice of words during her argument with Stolas, it seems she is very classist, as she is not only furious at his infidelity but also at his debasement in position, choice of lovers and actions, since she berated him for acting like a plebeian.

In fact, it's shown, in "The Harvest Moon Festival", that Stella is willing to go far as to actually have someone kill Stolas for cheating on her, not caring about who gets in the way.

In “The Circus” it shown that’s Stella always had a violent temper as a child. As a picture of her shown by Paimon having her attack two dog like demons. As an adult, she known to be rather snobby, arrogant and selfish because during the parties, she made nasty insults about Stolas to her friends not caring that he’s a few feet away from her to hear it. It also shown Stella can also be a bit heartless because she admits the only reason she comes back to the mansion is to torment Stolas.