The Dalek ship is huge; earth’s space shuttle would probably fit in one corner, looking like a tiny ornament. The Daleks were scary enough before, but being on their ship, surrounded by them, all Rose can do is cling to her faith in the Doctor, sure he won’t let her die.
Seeing his face on the viewscreen is immediately reassuring. He doesn’t look scared, or worried, he’s calm and confident, determined.
“I’m going to save Rose Tyler from the middle of the Dalek fleet.”
After that, he’ll save earth and destroy the Daleks.
Rose doesn’t doubt him for a second.