And she's taking big strides to keep up with Optimus, she's actually kind of fast for her size.

"... This Unit has scouted a reasonable area around the ruins," She replies, her attention focused directly in front of her instead of on Optimus.

"This Unit has also made attempts to enter planetary orbit, but it's systems seem to malfunction as it is drawn back to the planet." In other words, Miria is mistaking that nice call of Cybertron as a malfunction in her systems.