yeah - my read on this story, is a portrayal of different forms of loving a person, and how discrepancies in what Person A might recognize versus what Person B might recognize, can create issues that risk the breaking of a relationship between them--established or hypothetical.
Kaede requires that verbal affirmation - perhaps that has something to do with being an avid reader, with no real personal experience? Where so many stories, by virtue of being written down, rely on verbalized declarations between people in love, I could see an argument where Kaede has internalized that as the "way to express" one's emotions and intent.
But as you said - Momoka is very "show don't tell", and we know that blew up in her face with Shiori, after a fashion. Incongruent methods of expression one's feelings, but that first time, it wasn't surmounted, and things fell apart for her.
That, coupled with everyone in Momoko's life calling her doll-like for her apparent lack of expressiveness, and she'd have very mixed signals on whether she is expressing her feelings in a way they're understood.
But she tried all the same, and Kaede, for her part, was largely receptive and reciprocated by affirming Momoko as a person, and as a person worth loving.
The disconnect being that Kaede wanted that verbal affirmation in return, not recognizing Momoko's actions as the equivalent. She knew that Momoko was expressive, but didn't--or couldn't--interpret her actions as the love she sought.
Luckily - they both have made a point of communicating, and as you said, Momoko learned to not simply give up in the face of wanting something (from Kaede, no less), and so this chapter was the result.
Hopefully, assuming this continues past this bit, Kaede can learn Momoko's love language, and they learn how to communicate meaningfully even if their "voices" aren't identical.