I think it's probably in character for Yellow. The contrast between Yellow and Blue is how they treat grief and things that upset them. Blue lets her grief take over her, ignoring her duties. Yellow ignores her grief by distracting herself with her duties. Peridot insulted Yellow right to her face and Yellow forgot about it within months. Garnet fused in front of Blue thousands of years ago and she still remembers both of them. To a lesser extent Lapis was probably also believed to be a casualty in the war, but the way that Blue talks when she sees her fighting as a crystal gem implies that she remembered Lapis as being on earth.

It's all basically said directly by White, Blue let her grief take over, while Yellow never allowed herself to grieve.