spoilers for 14-18 Like, per the Kaede angst, her being burnt on love before makes perfect sense considering we know much the same of Nanami like, out the gate. Her breakup was the first chapter, as well as the confirmation she had been in another (likely) unsuccessful relationship with a woman before. You could conject, "just get married like normal" as a response to that burn, possibly, that remains to be seen, but she's already have some foil to Kaede. And throughout, Kaede's aspirations as a mangaka have always been her priority so it's no surprise she would think herself romantically unavailable, despite relying so heavily on Nanami emotionally. Currently, that is still attached to the aspiration, whereas Nanami has been able to detach it and see it for what it is, love. When that dream is on the cusp of fruition, and Nanami's sorrow is a palpable hurricane at the prospect of moving out, we will see Kaede follow suit. I trust this one to pan out, I really don't think it's that grim.
and besides if you're able to let whispering you a love song's melodrama slide, this is not a big deal, and far less on the "melo-" end.