"Could you not be alone with him, please?" "It makes me so anxious."
Color me surprised that Asuna isn't the one saying this
FWIW Natsuki specifically says 心配なの, and from looking it up "shinpai" can mean "worried" or "concerned" as well (anyone who watches anime is probably going to hear 心配するな sooner rather than later!). But some definitions I saw do list "anxious"/"anxiety", and considering the series seems to be heavy on "See, you thought you were the only one who felt like this, but I feel like it too! Whodathunk?", it seemed like "anxious" would be a better fit. Then "I'm anxious" -> "It makes me so anxious", so that it hopefully read a bit better/felt a bit more natural.
Not like I want to get into a "Here's why I picked word X" over everything, since, y'know, I'm not a proper translator... <_< but just as an example to show how I'm trying to do more than just parrot what Translate says.