The 180 days is the maximum period that a
visitor may remain in the UK. However, a visitor's stay is also limited to the
validity of the entry clearance. Interestingly, it's the
same as a Schengen visa. However, the UK is different to the US, where an Immigration Inspector determines the
duration of stay at the port of entry.
Moreover, if she had indicted that she intended to stay for three weeks but remained for five months, then she may have
problems as a genuine visitor in the future.
This is not intended to be legal or professional advice in any jurisdiction. Please click on any given
links for further information. Refer to the source of any quotes.