As others have said, she might have been an employee collecting wages and couldn't take her daughter inside. She was on the other side of the glass door holding onto the reigns.
It used to be the norm to leave prams outside shops and there was never a problem and as someone has already said, children were left outside pubs with a bottle of lemonade and a packet of crisps. I used to really envy them, my parents never went into pubs and it seemed so exciting!
big wow! left for "two to three minutes". i left phoebe outside the post office in her pram for longer than that last week. Is it less chavvy because it was the PO and not the bookies??