Suzie says

A Repeat after me: ‘No.’ ‘we’re committed this afternoon.’ ‘I’m not free today.’ You could also ask her to recognise that while you do sympathise with her plight, she needs to deal with you in the same way she would with professional help – pre-book and accept when it’s not available. She may be suffering from postnatal depression or simply stress, which is something her GP and health visitor could help with.