Yukari said she met the 2nd wife for the first time at the funeral but that may not be the case for 2nd wife who may have known about Yukari from the dead husband.
Or...
Second wife met Yukari first, then got together with the ex husband first in order to gain Yukari's time and sympathy after his "accident" and to also live comfortably with her using the inheritance from him. Just as planned.