The husband returned, but

I've brought something that will make you angry again.

This time, it's Brielle. I didn't write down what to call her...

Mistress/Homewrecker - Too much like a modern melodrama
Lover - Seems too lighthearted
Sweetheart - The word sounds affectionate for an affair
Concubine - Feels more like Joseon Dynasty Korea than a Western fantasy romance

I'm asking you, users. What should I call these kinds of characters?