All the TARDIS notices of Johnny's emotional revelation is his embarrassment, confusion, and his affection for her. Feeling that deepen in the moments after her kiss and her display pleases her, so she drops her hand from his shoulder to entwine her fingers with his while he looks up at the endless ceiling.

"It is," she agrees quietly and then Time rewinds, the angle of the view shifting until Earth comes into sight as a huge blue marble. "I miss it." Because this isn't what she can see in this universe at all, she can see almost nothing and feel even less of it. She sighs, even though this was supposed to cheer him up.