She can't is the first thing that comes to mind. Only Rose realizes she can but doesn't necessarily want to. These supplies could be given to people with better use for them than her. She could get by alright with what's already in her pack for now, so... She'll take the extras but doesn't plan on keeping them.

"Roger that!" she replies while beginning to stock up. "What are you going to do? Probably not a good idea to stick around here too much longer." Cue a conveniently timed groan from the hull of the ship with a flicker of dim lighting for extra effect. Hm, yes, it really sets the "we're all doomed" mood she has to say.