If her husband has not signed any Contract to sell the premises then there is no contract -no sale so no one has 'pulled out'.
She must be very thick (sorry) to have signed over her business and agreed to a price without her even realising it. However, if the deed is done she must get her Solicitor onto it asap to see how far she has got into the deal,
It is quite plausible that she has accepted to sell the business, but she could not have sold the property which does not belong to her, therefore if the valuation included the premises , and the buyter gave her a price for her business based on this, then she has the upper hand as the buyer will now be liable to purchase a business without premises, way over market price.