So... I kinda read it like Satoko was basically right about Yuka not actually being in love with her, but rather than her wanting to be nice to a friend or doing it out of obligation or whatever, it's that Yuka wanted to feel loved? Or that she was moved by Satoko's feelings and wanted to hold on to them? That's not a terrible place to start a relationship, and it certainly doesn't seem like Yuka's against being with a girl, but I don't know if it's terribly reassuring for the kind of insecurities Satoko has. In that case, I can see her worrying about whether anyone else would do just as well if they also confessed to Yuka, or if Yuka might find someone she actively wants to be with instead of just passively appreciating Satoko's feelings.
But that seems a little incongruously pessimistic and uncertain for the seemingly bright and cozy tone at the ending, so I don't know if that's actually what the author was going for. Not sure what to make of it.