Hi Julie60
It would depend on a number of factors such as the number of hours worked, any disabilities in the family.
Then is something on UC called work allowance, for single parents this is £344, then there is the earnings taper 55%.
I would advise your friend to contact a Welfare Rights Organisation and ask for a better off calculation;
advicelocal.uk or check their own entitlements using an on line benefit calculator;
gov.uk/benefits-calculators If your friend does start working they need to put a note on their journal otherwise they may be hit with an overpayment and a penalty charge.
Gary