Why does Vegeta tolerate Android 18?
The primary reason that Vegeta tolerates Android 18 is that he has changed.


He has become more human than a savage who destroyed planets for fun. This change of his is evident and there are many more instances of this in DBS (Dragon Ball Super). For example, in episode 2, he took a day out of his training schedule and went to the amusement park with Bulma and Trunks and the incidents that occur over there also highlight this sea change in his personality. 
In fact, he's in touch with his human emotions, an instance being when
he gets angry over Beerus slapping Bulma when she slaps him for
ruining her birthday party and makes up his mind to fight him whereas
till that point he had been swallowing up his pride and acting like a
clown (episode 7).
It can also be said that he now accepts things as they are. He
realized that he isn't the strongest out there, and has shifted his
focus to becoming the best. He also has realized that there is nothing going to be achieved by revenge, so he doesn't seek revenge anymore.


This explains why Vegeta tolerated Android 18.