In that case, you can either tune her out or change the subject - you know, just don't engage and hope she'll take the hint. Humour her - nod and smile and once again don't engage. Or take the bull by the horns and politely but firmly state that you are an adult, you appreciate that she cares and wants to help you, but you don't need to be told what do like a small child.
My mum has a tendency to do this, so I sympathise.