Hmmm, I would say if they have not initiated the conversation about how it affects you all socially and financially they're not great friends anyway. If you want them to find somewhere else for the next 3 months or longer if it extends again then that is the conversation you need to have.
Not necessarily, but reassess the situation via an adult conversation. You agreed to a month. It has been longer already with no clear end date. Talk to them and work out what works for you all. This might be them paying you. It might be them finding somewhere else to stay in the meantime. It might be something else.
I think that it's the OP's nerves which are suffering wear and tear, not the carpets. As has been said already, the petty squabbles will break out eventually and it will all end in tears.
Households mixing indoors has been against the law for several months now hasn't it? I'd worry less about the carpets and more who will be paying the Covid fines?
Essential Money | Who & Where are you? | Work & Benefits | Household and travel | Shopping & Freebies | About MSE | The MoneySavers Arms | Covid-19 & Coronavirus Support