Bellatrix Lestrange found herself caring for her lord while the rat was away establishing if the Weasley boy had returned to Hogwarts, she also found herself questioning her life choices. Before the Potter brat her lord was handsome and charismatic but with powerful, influential and utterly ruthless added to the mix. His death eaters were the badest people on the planet and kicked arse almost unopposed.
She couldn't help but compare that to there current situation where this creature, a one-armed one-eared witch and a wizard whose greatest talent was turning into a rat was all they had. They had no money, power or influence and were reduced to robbing muggle stores at night for food and necessities.
What really worried her was this creature thought that as soon as he returned to a body people would once more be flocking to worship at his feet, from Wormtail's experience and her own encounter in the Black family manor she seriously doubted that was going to happen. Bella was often accused of not playing with a full deck and this was an image she cultivated because she was a very smart lady, her name struck terror into her opponents, which always gave her an edge in a fight.
The fight at Grimmauld Place had greatly affected the witch, she wasn't sure if it was being seriously outmatched for the first time ever or the fact that she lost her dark mark along with her arm but Bella was now looking at things differently and not liking what she was seeing.
Her time in Azkaban was bad but she suspected her master's ordeal was a lot worse and that great intellect was now the wrong side of insane, with the current political atmosphere sweeping the country they had nothing to offer potential new recruits.
Bones had made it crystal clear, possessing a dark mark was a death sentence and would also see your possessions seized, a high price to pay for being encouraged to rape and torture a few muggles. Her master was certain all he had to do was kill Harry Potter and the world would shudder at his name before paying homage to the greatest wizard who ever lived, Bella suspected that even if he managed the task Potter would become a martyr that would unite everyone against her master.
She was between the proverbial rock and a hard place but her options were severely limited, there was no place in Britain that was safe for Bella and she had no funds to go anywhere else. She was tied to this creature that used to be her master by the simple fact that she had no other options open to her, she just wished Wormtail would hurry up as the creature really freaked the pureblood out and it was becoming harder to hide these feelings.