It's kind of expected story-wise for her to be freaked out a bit since 1)reality is really different from what she expected, 2)author's usually like putting in some sort of conflict and we're now a good bit in for some to finally show up and 3)rui's been shown to be a little too carefree, so of course she'd be worried for her friend, but I hope she can quickly see that shinobu's a good person and get over any prejudices sooner rather than later! Maybe even join in on the friendship a little bit lol