That probably would have been a good idea. Too bad she never got a sonic screwdriver of her own. If they needed it, she had her phone too, which would provide some light, so she got it out.
"Vashta Nerada are the shadows.. well they're in shadows. I've never come across them but they're swarming, carnivorous microscopic beings that you can't see. They're harmless in small amounts but if you see something that shouldn't have a shadow but it does.. that's them. They'll eat you alive. Literally." And just thinking about it gave her the shivers.
She took his hand gratefully and slid down the pile of rubble as well. "If you see something like that, it's best to stay in the light. And thank you.. for helping me down."