Most house-hunters probably never go anywhere near to an estate agent's window. Neither do they look on any particular estate agents' website. Instead they simply go to Rightmove.co.uk, PrimeLocation.com and/or Zoopla.co.uk. The vast majority of houses offered for sale appear on at least one of those sites, with many being listed on all three. (A lot of house-buyers probably never look anywhere other than on those three websites).
Sellers can't advertise directly on those websites, as they only accept adverts from recognised estate agents (and charge them fairly hefty fees for doing so). It's probably listings on those 'external' websites (rather than on the estate agent's own website) which your friend is being asked to consider paying for. If so (unless she's prepared to seek out another estate agent, who includes those external advertising fees within their percentage) she'd be mad to decline the offer, as she'd be losing well over 90% of potential buyers.