How can I tell my friend I don't want her to watch my son?

i think the best thing for you to do is to sit your friend down and in a very civilised manner let her know how you feel about her speaking to children and for that matter your child specifically like that. let her know she may speak to hers how she pleases but you believe in speaking to children with as much respect as you do an adult. let her know that you are not judging her or trying to say she is a bad parent in no way shape or form and you understand that it may be stressful for her to be raising her 4 children but that is no excuse for speaking to them in that way. let her know that you will not be letting her watch your child anymore and you hope that your decision does not affect or come in between your friendship its just that you feel as a parent that this is the right thing to do. i mean obviously if she speaks to your child in this manner when you are around imagine what she says or does when you are not. Your child should always come first and if she is angry about you telling her how you feel then may be you and her were not ment to be friends.she has her own way of disciplinary actions and so do you so just let her know how you feel in a very respectful way. hope this helps ;)