The context is that 美琴 is advising the listener not to approach another person (望) who is an acquintance with a bit of a bad attitude. 望 had gotten into an argument with another person. 望 was in the wrong but won't admit it. The listener does not know 望 well, but jokingly offers to teach her some manners. Then 美琴 says the above line.
At first I thought 美琴 was afraid that the listener would take offense to being called 下手. But now, based on the context, I'm thinking she's afraid that the listener will think "she's implying that 望 is a jerk and shouldn't be approached, how rude".
Can you tell which it is just based on the above sentence? How?