The last few chapters have focused on Yuna's anxiety and her doubts about the relationship. This creates tension and a sense of impending doom, but I'm not sure it signifies anything more than the (unhappy) state of Yuna's mind. When Rena suggested opening an independent salon, for instance, Yuna secretly worried about strangers in their home. But now that Rena is considering becoming a branch manager instead, Yuna sees only a threat to the "shared dream" she never really wanted in the first place.
Rena has worries, too, but the overall state of their relationship seems quite good. Nevertheless, Yuna continues to catastrophize everything, even Rena's understandable doubts about her career path. At this point, that tendency is the only visible threat to their relationship.