English Translation
She was alone there.
一人きり、二人きり… are common expressions. きり is derived from a verb 切る（きる; to cut）. きり means “exactly”, “just” or “not more and not less”. The image of きり is to cut off the bottom and the top in order to narrow down or specify the range.
Another example with きり is これっきり. – e.g.) 二人で会うのは、もうこれっきりにしよう。= This is the end. Let’s stop seeing each other. (i.e. a sort of “Dear John” letter). これっきり literally means “this is the last time, no more chance”.