Do you agree with Lee’s assertion that it doesn’t matter if Scott liked Mouth, as long as he was nice to him? What do you think she means by that?

In context, Mouth lacks self-esteem, has no real friends, and because of this he tries too hard. Not knowing what to do and feeling all alone, Mouth attempts to take his own life. Thus, Lee is referring to the fact that Scott didn't need to be Mouth's friend, as long as he didn't add to Mouth's doubts about himself.