Bella is very strange. She takes off the ring when she goes on a date with Tremolo and fucks, but she put it on the morning after sex. She says it's a habit, but she's obviously lying.
Jade never took off her rings during meetings with Tremolo and it's understandable why. She hates and despises her husband, for her sex with Tremolo is an attempt to amuse her ego and humiliate her husband in her eyes.
But not for Bella. For her, loyalty to James is very important. I even think she's pretty religious. She calls herself an adulteress and probably keeps her husband's things in that locked room. She was proud of her loyalty, but everything broke down when MС came into her life. Therefore, for me, the only explanation why she did not take off the ring was that she began to enjoy her depravity and betrayal to her husband, like Jade. Yes, she fucked him this morning with a ring on her finger.