I have an eleven year old who winds me up too and although I am not single now I used to be,so know how it feels.When you have a partner it is far easier to switch off and wind down,enaberling you to switch channel so to speak.

It may be good for her to put some time aside to give him some undisturbed attention as sometimes bad behaviour is a way of seeking out attention.A firm,consistant approach where boundaries are set and not changed helps too.She should tell him quietly but firmly that swearing is bad behaviour and that it would make her happy if he did not do it.Try not to shout as it will go over his head.I know only to well how hard it is not to shout but it will keep everyone calm if you do not.

Hope this helps.